scientific american - 1996 05 - the comets' lair

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OF THE SOLAR SYSTEM

Deadly mines threaten the innocent throughout much of the world

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The Horror of Land Mines

Physicians still do not

honor living wills

12

Medical trials in question The

fu-ture chess champion Biodiversity

and productivity What pigs think

16

CYBER VIEW

Broadcasting on a narrow medium

28

A tailless airplane Fake muscles,

real bones Wandering genes

30

PROFILE

Distinguished naturalist Miriam

Rothschild defies categorization

2

The Kuiper Belt

Jane X Luu and David C Jewitt

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Scientific American (ISSN 0036-8733), published monthly by Scientific American, Inc., 415 Madison Avenue, New York, N.Y.

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Software for Reliable Networks

Kenneth P Birman and Robbert van Renesse

The failure of a single program on a single

com-puter can sometimes crash a network of

intercom-municating machines, causing havoc for stock

ex-changes, telephone systems, air-traffic control and

other operations Two software designers explain

what can be done to make networks more robust

Social scientists have more often focused on anger

and anxiety, but now some are also looking at the

phenomenon of happiness They find that people

are generally happier than one might expect and

that levels of life satisfaction seem to have

surpris-ingly little to do with favorable circumstances

Finding invisible planets

From phonetic writing

About the Cover

Small blast mines of the type picturedcan be difficult to see on many terrains,which makes them a severe hazard forunwary civilians returning to formerbattle sites Painting by Daniel Adel

The Pursuit of Happiness

David G Myers and Ed Diener

98

MATHEMATICAL RECREATIONS

Fractal sculpture turns cubes into flowing spirals

102

3

Between 1866 and 1960, hunters caught more than

16,000 of these white whales Today only 500

re-main in the St Lawrence Although hydroelectric

projects have been blamed for their recent woes,

belugas’ great enemy now seems to be pollution

The Beluga Whales

of the St Lawrence River

Pierre Béland

The weapons complex near Hanford, Wash., made

plutonium throughout the cold war The U.S is

now spending billions to decontaminate this huge

site, yet no one knows how to do it or how clean

will be clean enough Second in a series

Confronting the Nuclear Legacy

Hanford’s Nuclear Wasteland

Glenn Zorpette, staff writer

The oared galleys of the Greeks once ruled the

Mediterranean, outmaneuvering and ramming

en-emy vessels Their key advantage, unknown for

centuries, may have been an invention rediscovered

by Victorian competitive rowers: the sliding seat

The Lost Technology

of Ancient Greek Rowing

John R Hale

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4 Scientific American May 1996

Pursuing what is merely not known, investigators sometimes find

what is not supposed to be For over 30 years, the quark seemed

to be the irreducible unit of nuclear matter Yet recently, when

physicists forced collisions between protons and antiprotons, they found

hints among the subatomic shrapnel that quarks might have an internal

structure, comprising even tinier entities How far down is the bottom?

Zoology has been rocked during this decade by the capture of several

large mammal species, some new to science, others that had been thought

extinct, including the Tibetan Riwoche horse and the Vietnamese Vu

Quang ox The pace of these discoveries is astonishing because only a

handful of big land beasts had been catalogued previously this century

Astronomers, meanwhile, have been turning up billions of additional

galaxies and the first examples of planets orbiting sunlike stars Much

closer to home, though, surprises havealso cropped up within our solar sys-tem Four years ago, after considerablepatient effort, Jane X Luu and David

C Jewitt found an entirely new class ofobject in the outer solar system It was

no more than an icy orb a few hundredkilometers across, but its existence ar-gued that a huge ring of similar bodiesextends out beyond Neptune Dozens

of additional objects have been foundsince then, confirming the presence ofthe long-sought Kuiper belt They haveshed light on the origin of comets andeven revised some astronomers’ thinking about Pluto, which may not be

a true planet at all Luu and Jewitt explain more fully in “The Kuiper

Belt,” on page 46

Speaking of finding treasures in uncharted spaces, everyone roaming

the Internet is encouraged to visit Scientific American’s new World

Wide Web site at http://www.sciam.com/ These days it is often hard to

confine the contents of our articles to just two dimensions; they keep

try-ing to pop off the page, grow like kudzu and intertwine with the rest of

the world What better place to let articles go, then, than on the Web,

where readers can enjoy this magazine in a more interactive, unconfined

form Visitors to our site will discover expanded, enhanced versions of

articles in the current issue, including links to other relevant sites on the

Web, “Explorations” of recent developments in the news, a “Gallery” of

images, sounds and animations that capture the beauty of science, and

much more We think you will find it to be the ideal springboard for

con-ducting your own explorations of the universe Happy hunting

JOHN RENNIE, Editor in Chief

editors@sciam.com

Unexpected Thrills

Established 1845

FR O M T H E ED I T O R S

THIS TINY COMET

may have recently emerged

from the Kuiper belt.

John Rennie, EDITOR IN CHIEF

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LIVE LONG, BUT PROSPER?

Richard Weindruch rightfully points

out that mouse data showing how

a restricted diet increases longevity

can-not be extended to humans at this time

[see “Caloric Restriction and Aging,”

January] But if the extrapolation is

val-id, look out, Social Security trust fund

If aging baby boomers like myself

de-cide to embrace a spartan lifestyle, we’ll

be around until the year 2060

ROBERT CORNELL

Lexington, Ky

Weindruch omitted any reference to

work that examined the effect of the

compound deprenyl [used in the

treat-ment of Parkinson’s disease] on the

lon-gevity of male rats These studies showed

an increase in both the average life span

and the maximum life span of these

rodents In other words,

pharmaceuti-cal intervention can also slow aging in

mammals

WALLACE E PARR

Stevensville, Md

Weindruch replies:

The concern raised by Cornell is

un-warranted: caloric restriction influences

not only the length of life but also the

quality of life If vast numbers of baby

boomers turn to caloric restriction, a

new society would likely emerge in

which energetic 85-year-olds change

ca-reers and Social Security would have to

be entirely restructured A Hungarian

re-searcher, Jozsef Knoll, did report

great-ly extended average and maximum

life-times in rats given deprenyl

Unfortu-nately, subsequent studies of the drug

have found either a very mild increase

in maximum life span or no effect at

all In contrast, caloric restriction

ex-tends maximum life span in a

repeat-able fashion worldwide

LOW-TECH SOLUTION

In “Resisting Resistance” [Science and

the Citizen, January], Tim Beardsley

states that “the attention being focused

on infectious disease indicates that a

turning point may be in sight in one of

humankind’s oldest struggles.” Absent

from the solutions discussed—includingnew infectious disease laboratories, moreintense surveillance and investigation,more prudent use of antibiotics and de-velopment of new drugs—is one majorpreventative component: hand washing

According to the U.S Centers for DiseaseControl and Prevention, “Hand wash-ing is the single most important means

of preventing the spread of infection.”

NOEL SEGAL

President, Compliance Control

Forestville, Md

MIXED REVIEWS

Thomas E Lovejoy, who reviewed

my book A Moment on the Earth

[“Rethinking Green Thoughts,” views and Commentaries, February], is

Re-a prominent proponent of the bleRe-ak vironmental outlook the book contests

en-Thus, Lovejoy has a professional interest in denying the book’s validity:

self-his work was criticized in the book, apoint only obliquely disclosed to read-ers Lovejoy’s enmity is indicated by sev-eral inaccurate statements He writesthat I extol the recovery of the bald ea-gle “while ignoring its previous down-ward trend.” Yet my chapter on speciesbegins by noting that DDT and loggingcaused the decline of the southern baldeagle Lovejoy says I do not credit Ra-chel Carson for inspiring environmen-tal reforms But on page 82, I write,

“Society heeded Carson’s warnings, acted the necessary reforms and real-ized such a prompt environmental gainthat the day of reckoning Carson fore-saw never arrived This shows that en-vironmental reform works.”

en-Lovejoy accuses me of “innumerableerrors” yet cites only two One is a sin-gle-word copyediting glitch, and the oth-

er, according to Lovejoy, is an “absurdassertion, building from a misunder-standing of evolutionary biologist LynnMargulis’s work that cooperation isdominant in nature.” In fact, I present

this notion as speculation: surely a

re-viewer for a science publication ought

to be able to make the distinction tween assertion and speculation Andgood or bad, it’s hard to believe mycharacterization of Margulis’s work is

be-“absurd,” as Margulis herself read thebook at the galley stage

Of course, hostile reviews are an pational hazard for writers Yet Love-joy’s resort to false claims suggests that

occu-he seeks to divert attention from toccu-hebook’s central contention: namely, thatmost Western environmental trends areimproving The optimism I propose may

be right or wrong, but the debate on itwill not go forward if magazines such

as Scientific American hand the concept

over to those with a dull ax to grind

in developing countries The book, infact, contains little mention of my work(which is mostly about tropical forestsand soaring extinction rates) and is crit-ical of it in only one instance My mainlament is that his book, which has somereally important points to make, doesnot make them better For example, toequate cooperation with Lynn Margu-lis’s work on symbiosis is simply an error

STRING THEORY

In quoting Pierre M Ramond, husree Mukerjee [“Explaining Every-thing,” January] deprived him of a su-perb simile She has Ramond sayingabout string theory research, “It’s as ifyou are wandering in the valley of a king,push aside a rock and find an enchantedstaircase.” Surely what was intended was

Mad-“wandering in the Valley of the Kings,”

a reference to the sarcophagal region ofEgypt that grudgingly yields its hermet-

ic secrets

HAROLD P HANSON

University of Florida at Gainesville

Letters may be edited for length and clarity Because of the considerable volume of mail received, we cannot answer all correspondence.

Letters to the Editors

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MAY 1946

Color television looms large on the radio horizon: RCA

has it but calls it impractical as yet; Columbia

Broad-casting System is going all-out for color; Zenith Radio says

that they will produce only color-television receivers; and the

public waits with more or less patience for the final outcome.”

“Predicating their conclusions on a price of $15 a ton for

coal, atomic energy experts recently predicted that atomic

en-ergy might economically come into competition with coal for

industrial power production in from three to twenty-five

years According to a director of the Bituminous Coal

Insti-tute, this quoted price is greatly excessive, and coal is now

being delivered to the power producers at a national average

price of less than $6 a ton; therefore it would be ‘something

like two or three generations before bituminous coal has

any-thing to fear from atomic energy.’ ”

MAY 1896

The first really practical solution to the problem of

artifi-cial flight has been made by Prof Samuel Langley, the

secretary of the Smithsonian Institution Prof Alexander Bell

describes the successful experiments, which were carried out

near Occoquan, Va., on May 6: ‘The aerodrome, or flying

machine, in question was of steel, driven by a steam engine It

resembled an enormous bird, soaring in the air with extreme

regularity in large curves, sweeping steadily upward in a

spi-ral path, until it reached a height of about 100 feet in the air,

at the end of a course of about a half mile, when the steam

gave out and the propellers which had moved it stopped

Then, to my further surprise, the whole, instead of tumbling

down, settled as slowly and gracefully as it is

possi-ble for any bird to do.’ The supporting surfaces

are but fourteen feet from tip to tip.”

“Sound reproducing machines are no

less wonderful than sound

transmit-ting apparatus, and, although the

talking machine may not

find as wide a field of

application as the

telephone, it is perhaps more interesting and instructive Ourpresent engraving illustrates the gramophone in its latest form,the work of the inventor Mr Emile Berliner It is driven by abelt extending around the larger pulley on the crank shaft,which is turned by hand On the turntable is placed the hardrubber disk bearing the record The sound box is mounted on

a swinging arm, which also supports the conical resonator.With five minutes’ practice a child can operate it so as to re-produce a band selection or a song in perfect tune.”

“Each year the laws of sea storms are understood more fectly through the indefatigable efforts of the United Stateshydrographic office The landsman hardly appreciates whathas been done by the government to protect ships from dan-ger In order to measure the storms, it was necessary to obtainreliable data from a wide extent of ocean territory In the ab-sence of telegraph stations, forms for keeping observationswere issued to every captain of a vessel touching any Americanport, to be filled out and mailed to the headquarters at Wash-ington In return for this labor every captain received free theMonthly Pilot Chart From the pile of data received, a map

per-of each storm was constructed, and rules were compiled thatare given to mariners when encountering a storm at sea.”

“The Medical Society of Berne has inaugurated a plan forthe suppression of press notices of suicides, as it has been ob-served that epidemics of suicides, so called, come from ‘sug-gestion,’ acquired through printed accounts of them.”

so exquisitely wrought and transparent as to inducethe belief, at first sight, that it has been stuck on, in-stead of being painted on a flat surface.”

“There is evidently an abundance of caloric in the commonelements, and which might be had at a cheap rate, could webut find a cheap and ready method of liberating it from its la-tent state; and the time may yet arrive, in which water will be

found to be the cheapest fuel, and be made to furnish bothheat and light Latent caloric is commonly called ‘latent

heat,’ but we think it is not heat in any sense, until it is

liber-ated and becomes palpable.”

“It is urged upon emigrants to Oregon to take wives withthem There is no supply of the article in that heathen land.”

50, 100 and 150 Years Ago

The new talking machine

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When the U.S Congress

passed the Patient

Self-Determination Act in

1990, many ethicists hailed it as an

im-portant step in the right of patients to

choose how they are treated—and how

they die The possibility that the act

might reduce health care costs by

cut-ting down on futile and unwanted

treat-ments was seen as an added bonus It

has been estimated that almost 40 percent of all deaths in the

U.S take place following the withdrawal of life-sustaining

treatments—often from a sedated or comatose patient and

af-ter protracted, agonizing indecision on the part of family

members and physicians

The Patient Self-Determination Act was designed to reduce

this indecision by giving patients more control over their

des-tiny It requires hospitals to inform patients and their

fami-lies—upon a person’s admission to the hospital—of their legal

right to refuse various life-sustaining technologies and

proce-dures through what are called advanced directives The two

most common advanced directives are living wills, in which

individuals specify their choices concerning life-sustaining

treatment, and documents authorizing a spouse, relative or

other proxy to make such decisions, in the event that an vidual becomes mentally incapacitated

indi-So far the act and advanced directives have not had the pact that proponents had hoped for Only 10 to 20 percent

im-of American adults, at most, have signed an advanced tive Moreover, as a number of recent court decisions illus-trate, conflicts and misunderstandings still arise between pa-tients, relatives and health care providers over the propertreatment of critically ill patients

direc-Although some right-to-die advocates say that advanceddirectives can still fulfill their promise, others have theirdoubts Arthur L Caplan, director of the Center for Bioeth-ics at the University of Pennsylvania, predicted in 1990 thatadvanced directives and the Patient Self-Determination Act—

News and Analysis

have furthered the cause

of death with dignity

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and the notion of “patient empowerment” from which they

stem—would prove to be a failure Unfortunately, he says,

re-cent events have proved him right

The “nail in the coffin,” Caplan notes, is a paper published

last November in the Journal of the American Medical

Asso-ciation The article presented the results of an experiment

called SUPPORT, for Study to Understand Prognoses and

Pref-erences for Outcomes and Risks of Treatments The

four-year study, which involved more than 9,000 patients at five

hospitals, had two phases

The initial, two-year phase of the study revealed

“substan-tial shortcomings in care for seriously ill hospitalized adults.”

More often than not, patients died in pain, their desires

con-cerning treatment neglected, after spending 10 days or more

in an intensive care unit Less than half of the physicians

whose patients had signed orders forbidding

cardiopulmo-nary resuscitation were aware of that fact During the second

phase of the study, each patient was assigned a nurse who had

been trained to facilitate communication between patients,

their families and physicians

in order to make the patients’

care more comfortable and

dignified The intervention

failed dismally; the 2,652

pa-tients who received this

spe-cial attention fared no better,

statistically speaking, than

those in the control group or

those in the previous phase

of the investigation

But given that doctors are

the supreme authorities in

hospitals, says Nancy

Dub-ler, an attorney who heads

an ethics committee at the

Montefiore Medical Center

in Bronx, N.Y., it was

inevit-able that the nurse-based

tervention method employed by the study would fail She

in-sists that her own experience has shown that advanced

direc-tives can work—and particularly those that appoint a proxy,

who can provide more guidance in a complex situation than

can a “rigid” living will

“I definitely feel advanced directives are useful,” concurs

Andrew Broder, an attorney specializing in right-to-die cases

Broder recently served as the lawyer for a Michigan woman,

Mary Martin, who wanted to have a feeding tube removed

from her husband, Michael Martin, who had suffered severe

brain damage in an accident in 1987 Michael Martin’s

moth-er and sistmoth-er opposed the removal of the life-sustaining

treat-ment Michigan courts turned down Mary Martin’s request,

and in February the U.S Supreme Court refused to hear her

appeal An advanced directive “might have made the

differ-ence” in the Martin case, Broder says

Some ethicists fear that the problems revealed by SUPPORT

will spur more calls for physician-assisted suicide, the legal

status of which has been boosted by two recent decisions In

March a jury ruled that Jack Kevorkian, a retired physician

who has admitted helping 27 patients end their lives, had not

violated Michigan state law (Kevorkian still faces another

trial on similar charges.) That same week, a federal court of

appeals struck down a Washington State law prohibiting

eu-thanasia Oregon has already passed a law permitting

assist-ed suicide (although it has not come into effect), and eightother states are considering similar legislation

“I see suicide as a symptom of the problem, not a solution

to the problem,” says Joseph J Fins, a physician and director

of medical ethics at New York Hospital The lesson of PORT, he says, is that doctors must learn to view palliativecare—which focuses on the relief of suffering rather than oncuring disease—as an important part of their job Many phy-sicians, Fins elaborates, need to become more aware of devel-opments in the treatment of pain, such as alternatives to mor-phine that do not cause constipation, nausea, grogginess orother unpleasant side effects If doctors take these steps, Finscontends, horror stories about terminally ill patients beingsubjected to unwanted treatment should diminish, and soshould calls for assisted suicide

SUP-Officials from Choice in Dying—a New York City–basedgroup that created the first living wills almost 30 years ago(but does not advocate assisted suicide)—believe the prob-lems identified by SUPPORT can be rectified through more

regulation, litigation and ucation According to execu-tive director Karen O Kap-lan, Choice in Dying plans

ed-to further its cause with adocumentary that will beaired by the Public Broad-casting Service this summer;with a page on the WorldWide Web that will includeliving-will and proxy formsand educational materials;and with an electronic data-base that hospitals can con-sult to determine whether apatient has an advanced di-rective The group also ad-vocates legislation that wouldencourage physicians to bring

up the issue of advanced directives with patients as a routinepart of their care, rather than in a crisis

Kaplan hopes the threat of lawsuits may force hospitals topay more heed to the wishes of patients and their relatives.This past February, she notes, a jury in Flint, Mich., found that

a hospital had improperly ignored a mother’s plea that hercomatose daughter not be placed on a respirator The hospi-tal was ordered to pay $16 million to the family of the wom-

an, who emerged from the coma with severe brain damage.But there is no “ideal formula” for preventing such incidents,according to Daniel Callahan, president of the Hastings Cen-ter, a think tank for biomedical ethics These situations, hesays, stem from certain stubborn realities: most people are re-luctant to think about their own death; some patients andrelatives insist on aggressive treatment even when thechances of recovery are minuscule; doctors’ prognoses forcertain patients may be vague or contradictory; and families,patients and health care providers often fail to reach agree-ment on proper treatment, despite their best efforts

Callahan notes that these problems can be resolved only bybringing about profound changes in the way that the medicalprofession and society at large think about dying “We thought

at first we just needed reform,” Callahan wrote in a special

issue of the Hastings Center Report devoted to SUPPORT “It

is now obvious we need a revolution.” — John Horgan

News and Analysis

RELATIVES OF INCAPACITATED PATIENTS may disagree over when to withdraw treatment.

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Genetic mutations account for

a number of neurological

dis-orders, among them certain

forms of mental retardation By

study-ing such illnesses, scientists have learned

a great deal about normal brain

devel-opment Now they have new material

to work with In a recent issue of

Neu-ron, Boston researchers from Beth

Is-rael Hospital and Harvard MedicalSchool described a genetic marker for arare form of epilepsy called periventric-ular heterotopia (PH) Some 0.5 percent

of the population have epilepsy, andfewer than 1 percent of them have PH

“The disease seemed to be expressedexclusively in females, and these fami-lies seemed to have a shortage of malebabies,” says team member ChristopherWalsh “So there was the suggestion that

it was an X-linked defect.” The groupexamined blood samples from four af-fected pedigrees and quickly confirmedthe hypothesis They singled out a com-mon stretch of DNA along the X chro-

mosome that contained many

well-known genes, including one dubbed L1 Genes such as L1 that ordinarily help

to assemble the brain are strong suspects

in the search for PH’s source, Walsh

adds Damage to L1 itself causes an

ar-ray of developmental disorders oftenmarked by some subset of symptoms,including hydrocephalus (water on thebrain), enlarged ventricles, enlargedhead, thinning of the corpus callosum,retardation, spasticity in the lower limbs,adducted thumbs and defects in cell mi-gration PH also produces certain tell-tale brain defects In particular, neuronsthat should travel to the cerebral cor-tex—the outermost region of the brain—

News and Analysis

F I E L D N O T E S

Plotting the Next Move

Iam at the IBM Thomas J Watson Research Center in

Yorktown Heights, N.Y., talking to four of the six brains

behind Deep Blue, perhaps the second-best chess player in

the world Present are Feng-hsiung Hsu and Murray

Camp-bell, who began working on chess-playing computers as

graduate students at Carnegie Mellon University in the

1980s; Chung-Jen Tan, manager of the chess project; and

software specialist A Joseph Hoane, Jr Absent are Jerry

Brody, a hardware designer who

has been delayed by an ice storm,

and Deep Blue’s silicon brain—a

pair of refrigerator-size, 16-node,

parallel-processing computers—

which is housed elsewhere in the

building

In one corner of the room stands

a case crammed with trophies won

by Deep Blue and its ancestors,

ChipTest and Deep Thought, which

were created by Hsu, Campbell and

others (Deep Thought mutated less

than two years ago into Deep Blue,

a reference to the color of IBM’s

trademark.) Draped across one wall

is a banner announcing the match between Deep Blue and

world champion Garry K Kasparov in Philadelphia this past

February Deep Blue won the first game but lost the match

The IBM team wants to dispel one ugly rumor: Deep Blue

did not lose the match because of human error—namely,

theirs They did indeed tinker with Deep Blue’s program

be-tween its only victory in game one and its loss in game two,

but those changes had no adverse effect on the

contend-er’s play Oh, sure, in retrospect they would have been

bet-ter off if they had accepted Kasparov’s offer of a draw in

game five (as was the case in games three and four), which

he went on to win “If we’d won, everybody would have said

we were brilliant,” Campbell says

When Marcy Holle, an IBM public relations

representa-tive, suggests that the team explain why Deep Blue madecertain moves in its game-one victory, they look at her du-biously They remind her that the computer’s program is socomplex that even they do not really understand how it ar-rives at a given decision Indeed, sometimes the machine,when faced with exactly the same position, will make a dif-ferent move than it made previously

In three minutes, the time allocated for each move in aformal match, the machine can evaluate a total of about 20billion moves; that is enough to consider every single possi-ble move and countermove 12 sequences ahead and se-lected lines of attack as much as 30 moves beyond that

The fact that this ability is still notenough to beat a mere human is

“amazing,” Campbell says The son, Hoane adds, is that masterssuch as Kasparov “are doing somemysterious computation we can’tfigure out.”

les-IBM is now negotiating a match with Kasparov, who is ap-parently eager for it “He got moreexposure out of the match thanany other match” he has played,Tan remarks Kasparov also won

re-$400,000 of the $500,000 prizeput up for the event by the Associ-ation for Computing Machinery

In the October 1990 issue of Scientific American, Hsu,Campbell and two former colleagues predicted that DeepThought might beat any human alive “perhaps as early as1992.” Reminded of this prophecy, Campbell grimaces andinsists that their editor had elicited this bold statement Notsurprisingly, no one is eager to offer up another such predic-tion If they had truly wanted to beat Kasparov, Tan says, theycould have boosted Deep Blue’s performance by utilizing a128-node computer, but such a move would have been tooexpensive The goal of the Deep Blue team has never been tobeat the world champion, he emphasizes, but to conduct re-search that will show how parallel processing can be har-nessed for solving such complex problems as airline schedul-ing or drug design “This is IBM,” Holle says —John Horgan

X MARKS THE SPOTS

Researchers find a genetic marker

for an uncommon form of epilepsy

NEUROSCIENCE

DEEP BLUE’S HANDLERS:

(from left) Brody, Hoane, Campbell, Hsu, Tan.

Trang 10

remain deep inside the organ instead.

“We wondered why some of all celltypes [in PH] failed to migrate, as op-posed to all of one cell type,” Walshnotes “We think the answer is that thefemale brain is a mosaic.” One of thetwo X chromosomes in each cell of afemale fetus is shut off at random afterthe first third of gestation, he explains

So those with PH probably express mal X chromosomes in most cells andmutants in a few others As a result, se-lect representatives of all types of corti-cal cells are stalled in their movement

nor-In contrast, affected male fetuses, whichpossess single, flawed X chromosomes

in every cell, develop so abnormally thatthey are miscarried

Finding the precise gene should make

it easier to diagnosis PH, Walsh says

Most patients have no outward toms other than frequent epi-

symp-leptic seizures, which are ally atypical Also, whatevermechanism prompts PHmay play some role in otherforms of epilepsy “Theremay be hundreds of gene mu-tations that confer risk forepilepsy,” Walsh states (In-deed, geneticists from Stan-ford and the University ofHelsinki reported in Marchthat mutations in the geneencoding for a protein calledCystatin B occurred in an-other uncommon inheritedepilepsy, progressive myclo-nus epilepsy.) “But perhapsthe gene products behind PH

usu-do something throughout thebrain that causes seizures,”

Walsh adds, “and perhapsthat same thing underlies allforms of epilepsy.”

In fact, the products of chromosome genes control-ling development may standbehind even more neurologi-cal disorders than has beenbelieved Researchers at the J C Self Re-search Institute of the Greenwood Ge-netic Center in South Carolina are cur-

X-rently screening for L1 defects among

the 40 to 50 percent of mentally

retard-ed individuals in the state for whom nodiagnosis has been found To narrowthe search, the group limited the survey

to men having enlarged heads and ticity in their gait Already they have

spas-found a greater incidence of L1 tions than expected “L1-related retar-

muta-dation is not as prevalent as fragile-X

[another form of retardation],” saysCharles Schwartz, director of the Mo-lecular Studies unit, “but it’s probablystill more common than previouslythought.”

Knowledge of the actual molecular

mechanisms behind L1-related

disor-ders has recently given workers insightinto fetal alcohol syndrome as well Sev-eral years ago Michael E Charness ofHarvard University noted several simi-larities between certain aspects of fetalalcohol syndrome, his area of expertise,

and L1 disorders Therefore, he tested

the effects of alcohol on the L1 cule, known to guide axon growth overlong distances and connect neuronsduring development

mole-Last month, Charness released resultsshowing that alcohol completely abol-ishes L1’s adhesive properties in low

doses—namely, amounts that would bepresent in a pregnant woman’s blood-stream after she consumed one or twodrinks “Epidemiologists have suggest-

ed that there may be measurable effects

of low amounts of alcohol on a fetus,”Charness states “This finding provides

us with one potential molecular nism behind that observation.” The hope

mecha-is that the unraveling of more such anisms will lead to prevention or to bet-ter treatment for a wide range of neuro-logical birth defects —Kristin Leutwyler

mech-News and Analysis

Record Time

Far from the Olympic trials, three

teams of computer scientists have set

a new speed record—one that no one

thought would be reached before the

year 2000 Each group—from Fujitsu,

Nippon Telegraph and Telephone, and

AT&T Research and Lucent

Technolo-gies—transmitted in a single second

one trillion bits of data, or the amount

of information contained in 300 years’

worth of a daily newspaper They sent

multiple streams of bit-bearing light,

each at a different wavelength,

through a relatively short optical fiber

The technique should make

communi-cations cheaper

Monkey See, Monkey Count

At least to two, says Marc D Hauser

of Harvard University He and his

col-leagues tested how well wild rhesus

monkeys could add To do so, they

reenacted an experiment

done on human infants

That study found thatbabies stared longer

at objects in front ofthem if the number ofobjects differed fromwhat they had justseen So Hauser pre-sented monkeyswith a seeming-

ly empty box,which hadone side removed, and then replaced

the side panel while they watched

Next he put two eggplants inside the

box in such a way that when he lifted

the side panel again, only one purple

fruit appeared The monkeys stared in

astonishment—proving their

arith-metic ability

DOD ’s Toxic Totals

The Department of Defense came

clean this past March, announcing

that during 1993, 131 military

installa-tions around the country released 11.4

million pounds of toxic chemicals The

report was the first of its kind filed

un-der a feun-deral law that also requires

pri-vate companies to list such releases

The DOD says it has reduced

hazard-ous-waste disposal by half since 1987

and intends to make further cuts The

latest figures compare with some 2.8

billion pounds of toxic waste emitted

by civilian manufacturing companies

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To find out whether a daily dose

of aspirin prevents heart tacks, you take 10,000 peoplefrom the general population, select half

at-of them at random to take aspirin everyday, and follow all 10,000 for five or 10years to see how their cardiovascularsystems hold up This kind of random-ized selection is at the center of the clin-ical trials used to test all manner of newmedical treatments In practice, howev-

er, it may be significantly flawed

Kenneth P Schulz of the Centers forDisease Control and Prevention and hiscolleagues have been raising questionsabout the quality of “allocation con-cealment”—the process of hiding infor-mation about which patients will be as-signed new treatment versus which willget conventional care For instance, ifdoctors know that all new patients reg-istered on odd-numbered days get a newdrug that is under investigation, where-

as those registered on even-numbereddays get a placebo, they could easily re-arrange their appointment books—withonly the best interests of their patients

at heart—to undermine the intent of arandomized trial Even when there isnegligible evidence, doctors tend to be-lieve they know what treatment is mosteffective, Schulz contends

Researchers generally use

significant-ly more sophisticated methods to cate their patients, but the doctors whoactually carry out trials may go to evengreater lengths to subvert concealment.Schulz surveyed his co-workers anony-mously and found that some will doanything—from opening sealed enve-lopes or holding them over a strong light

allo-to rifling a colleague’s desk—for copies

of the randomization sequence

According to work that Schulz and

his collaborators published in the

Jour-nal of the American Medical tion, trials with inadequate conceal-

Associa-ment—half or more of those studied—yield estimates of effectiveness that onaverage are roughly 30 percent higherthan those where allocation is properlycontrolled In some trials, however, theeffect of cheating can work against atreatment’s apparent effectiveness, Schulzsays: medical staff convinced that a newdrug would not be in testing if it didn’twork may try to help their sickest pa-tients by sneaking them into the treat-ment group instead of the control group.The drug would then have to be signifi-cantly better than conventional treat-ment just to appear equal in efficacy.Such irregularities highlight the im-portance of good statistical analysis ofany difference between control and treat-ment groups Schulz analyzed one set ofpapers and found that only 2 percent oftests indicated “statistically significant”differences between control and treat-ment patients Because a statisticallysignificant result is defined as one thatwould appear by chance one time in 20,the 2 percent figure immediately putsthose trials’ methods in doubt, he says.Why do doctors who agree to enrolltheir patients in clinical trials turn aroundand effectively subvert them? “They un-

News and Analysis

NOT SO BLIND, AFTER ALL

Randomized trials—the linchpin

of medicine—may often be rigged

MEDICINE

It is the most famous equation of all time: EL = mc2 What is that “L” doing there?Working in 1912, Albert Einstein quickly decided that his equation was weightyenough without superfluous constants, so he crossed the “L” out But Sotheby’sthought Einstein’s deletions were quite valuable; it expected the manuscript to fetch

$4 million to $6 million At the auction on March 16, however, the highest bid onlybroached the $3-million mark, so the document was sold privately—for less—a fewdays later It will be donated to the Israel Museum in Jerusalem —Charles Seife

Cigarettes, it now seems, snare their

catch twice Not only does nicotine

raise levels of dopamine, a chemical

linked to addictive behaviors, but

an-other psychoactive substance in

cigarette smoke—

one not yet tified—reinforcesthat grip by inhibit-ing monoamine oxi-dase B (MAO B),

iden-an enzyme that grades dopamine

de-Looking at PETscans, Joanna S

Fowler and her leagues at Brook-haven NationalLaboratory foundthat MAO B was

col-40 percent less tive in smokers(middle) than inpeople who hadnever or no longersmoked (top) Fur-ther study showedthat the MAO Bdeficiency in smok-ers was comparable to that seen in pa-

ac-tients taking L-deprenyl, a drug used to

ameliorate Parkinson’s disease

(bot-tom) The finding may explain why few

smokers acquire the debilitating

condi-tion, brought on by low dopamine

lev-els It could also elucidate the

connec-tion between smoking and depression,

which is often treated with MAO

inhibitors

Drafting Ants

Ant fans have always presumed that

caste quotas in colonies remained

more or less fixed: communities

pro-duced however many workers or

sol-diers were required to fulfill their

needs But it now seems that one

spe-cies of ant makes more soldiers than

normal when threatened by an enemy

attack Luc Passera and his

col-leagues at Paul Sabatier University in

Toulouse, France, separated two

colonies of Pheidole pallidula using a

wire mesh The structure allowed legs

or antennae to pass through but

pre-vented any direct combat Both

col-onies quickly churned out more

“ma-jor” members, larger than the rest and

ready to defend them This

reproduc-tive tactic takes more energy and time

than would, say, recruiting troops from

Trang 12

News and Analysis

A Peek at Pluto

The Hubble Space Telescope has

cap-tured pictures of Pluto’s frosty

sur-face—66 years after the planet was

discovered The smallest,outermost member ofour solar systemsports a prominentpolar ice cap, a darkstrip bisecting thecap, a curious brightline, rotating brightspots and a cluster ofdark areas These fea-tures suggest thatPluto is not, as hadbeen proposed, a twin

of Neptune’s moon ton A computer pro-cessed Hubble data toproduce these images; other

Tri-graphics are available at http://www

stsci.edu/pubinfo/PR/96/09.html

He Said, She Said

Scientists at Johns Hopkins University

have found one reason why women

of-ten possess better verbal skills than

men do The group took MRI scans of

43 men and 17 women and compared

the gray matter in two brain regions

in-volved in verbal fluency Although the

women’s brains were on average much

smaller, in both language areas they

bore greater concentrations of gray

matter than the men did: 23.2 percent

higher in the dorsolateral prefrontal

cortex and 12.8 percent higher in the

superior temporal gyrus

FOLLOW-UP

Slowing Japan’s Fast-Breeder Program

After devoting three decades to

devel-opment, Japan has had to deactivate

its only fast-breeder reactor—one that

produces more plutonium fuel than it

consumes The prototype suffered a

dangerous leak of sodium coolant last

December, confirming many people’s

fears about its safety (See January

1996, page 34.)

Summer at the South Pole?

Long ago Antarctica may not have

been an icy mound Recent finds

sug-gest that it was once quite balmy

While searching for fossils some 300

miles from the South Pole, geologists

happened on an unusual growth There,

buried under layers of rocks, they found

a bed of moss that dates back at least

three million years (See November

1995, page 18.) —Kristin Leutwyler

derstand the need for randomization on

a cognitive level,” but the gut feeling for

it eludes them, Schulz explains As a sult, once a treatment has become re-spectable, it may be impossible to deter-mine whether it actually works WhenCanadian physicians explored the effec-tiveness of episiotomy to aid childbirth,

re-he notes, a third of doctors employedthe operation in 90 percent of the pa-tients ostensibly slated for the surgeryonly as a last resort

It can be difficult for doctors ted to the best possible care for their pa-tients to give medical decisions over to

commit-a roll of the dice, especicommit-ally if ecommit-arly sults from a new treatment are promis-ing, but it may be necessary “If youthink you know what’s happening, you’llnever allow it to play out, and you’ll nev-

re-er know But your notions aren’t based

on good data,” Schulz observes He

re-calls one randomized trial of rial cream given to prevent prematurebirths caused by vaginal infections: af-ter initial indications that the creamwas effective, reviewers moved to blockthe trial on the grounds that it would beunethical to withhold treatment—butwhen all the results were in, the controlgroup had had fewer premature births.Schulz and other medical statisticiansaround the world have developed guide-lines, to be published later this year, forreporting safeguards, including the meth-ods used in trials to ensure allocationconcealment Several major medical jour-

antibacte-nals, including the Lancet and the New

England Journal of Medicine, are

pro-posing to reject manuscripts that do notconform, so that trials whose results areeasily susceptible to jiggering will not bewidely published and become part ofwhat everybody knows.—Paul Wallich

A N T I G R AV I T Y

Pork Barrel Science

Between stints as prime minister,Winston Churchill retired to acountry farm, where he was fond oftaking walks with his grandson Heespecially liked the pigs, his grand-son remembered in a recent televi-sion interview One day the elderChurchill stopped to stroke the pigs’

backs with the end of his walkingstick “A cat looks down upon a man,and a dog looks up to a man,” the No-bel Prize–winner confided to hisgrandson “But a pig will look a man

in the eye and see his equal.”

Stanley E Curtis, professor of animalsciences at Pennsylvania State Uni-versity, intends to find out whetherChurchill was right In a pig-nutshell,Curtis wants to know what swineknow, and more “In particular, wewant to know how the animals feel,

not how a human being might thinkthey feel,” Curtis says “And we haveevery reason to believe that they don’tsee the world as we see the world.”Curtis plans to explore what goes

on in a pig’s mind’s eye, using a nology already established for thestudy of the mental capacities of pri-mates, including teenagers: videogames Of course, we can easily oper-ate joysticks; Curtis intends to modi-

tech-fy technology so that pigs, using theirsnouts, can interact with videos (Be-cause pigs are notoriously nearsight-

ed, a choice of glasses, contacts orradial keratotomy needs to be made.)Assuming all those problems getpig-ironed out, we can start to fathomwhat they fathom Because pigs have

at least six calls, Curtis’s ultimatedream is to determine the behavioralcontexts of their individual yelps: “Iwould see the day when we could usesynthesized calls from computers toengage in conversations with them intheir own language.” The result could

be pig husbandry’s version of the kind

of enlightened management manycredit for the rebound of the BigThree automobile manufacturers

“If we could have the pigs selves participate on the teamthat’s designing the piece

them-of equipment or the

facili-ty that they’re living in,that would be great,” Cur-tis says But what if thecommunication we get is

“Porkers of the World,Unite”? —Steve Mirsky

In Brief, continued from page 20

Trang 13

That biodiversity is valuable

enough to pay for itself has

long been recognized as a

self-evident truth Roughly half the drugs in

clinical use are estimated to derive from

nature The Biodiversity Convention,

adopted in 1992 at the United Nations

Conference on Environment and

Devel-opment, tried to ensure that profits from

such goods return to the place of origin

to aid conservation and local

communi-ties Despite some success, that goal

re-mains elusive Although

bioprospec-tors—those who seek potential products

in biota—number in the hundreds, the

returns they promise to peoples in

devel-oping countries appear highly variable

“I’ve seen genuine outrage in parts of

the world,” attests Daniel M Putterman,

a consultant who helps developing

coun-tries negotiate deals with industry The

anger is cutting off parts of the world to

bioprospectors In Thailand, public ire

has forced a British foundation to stop

seeking the medicinal secrets of Karen

tribes In India, thousands of insects

found in the luggage of two German

“tourists” have prompted legislation

regulating gene transfer; the Philippines

recently passed just such a law

Even when they agree to the transfer

of such resources, some Third World

representatives remain uneasy about the

power balance with their First World

partners “If you are a small fish

swim-ming with a shark,” says Maurice M

Iwu of the Bioresources Development

and Conservation Program in

Camer-oon, “it makes no difference if the shark

has good intentions.”

These problems center on that special

attribute of biological materials: they

reproduce Thus, a handful of seeds or

micrograms of microbes might be

enough to carry a genetic resource out

of a country Technological advances

allow tiny amounts of material to be

screened, so a drug developer may

nev-er have to return to the source country

“The trick right now is monitoring the

flow of material,” explains Walter V

Reid of the World Resources Institute

When a benefit-sharing agreement is

SOWING WHERE

YOU REAP

Profits from biodiversity are neither

easy to pinpoint nor to protect

POLICY

Trang 14

signed, local institutions must often rely

on the integrity of the foreign partner in

sharing information “You have no way

of knowing” what happened to a

sam-ple, notes Berhanu M Abegaz of the

University of Botswana On occasion, a

drug developer may offer to cultivate a

plant in the source country, Abegaz says

Nevertheless, he adds, this arrangementcan have a double edge: the firm thatholds the patent can also control theprice paid to farmers, and the produc-ers are kept at a subsistence level

The more land brought under

cultiva-tion, the greater may be the threat tobiodiversity And if collected from thewild, the plant itself may become endan-gered That happened with the Pacificyew, which yields the anticancer agenttaxol If a drug can be synthesized in thelaboratory, the pressure on biodiversity

News and Analysis

Certain gases in the atmosphere allow visible light to

pass through, but they block much of the heat

reflect-ed from Earth’s surface—in the same fashion as the glass

windows in a greenhouse Without this greenhouse effect,

worldwide temperatures would be lower by 35 degrees

Cel-sius, most of the oceans would freeze, and life would cease

or be totally altered According to the theory of global

warm-ing, an increase in greenhouse gases in the atmosphere will

produce unacceptable temperature increases A doubling of

the volume of gases, for example, would cause temperatures

to go up by 1.5 degrees C or more, a phenomenal change

by historical standards

The most dramatic consequence of the warming would

be a rise in sea level from the melting of polar ice caps, a

rise that the Environmental Protection Agency projects to

be 20 feet as early as the year 2300—sufficient to submerge

large parts of coastal cities Global warming would result in

profound shifts in agriculture and may, as some have

sug-gested, hasten the spread of infectious diseases

Aside from water vapor, the principal greenhouse gases

are carbon dioxide, resulting from the burning of fossil fuels;

methane, produced by the breakdown of plant materials by

bacteria; nitrous oxide, produced during the burning of fossil

fuels and by the decomposition of chemical fertilizers and

by bacterial action; and chlorofluorocarbons, used for

indus-trial and commercial purposes, such as air conditioning Of

these, carbon dioxide is the most important The

atmospher-ic concentration of CO2was 280 parts per million before

the Industrial Revolution; with the increasing use of fossilfuels, it has risen to more than 350 parts per million today.The idea of global warming gained support as tempera-tures soared to record levels in the 1980s and 1990s, butthere are several problems with the theory, including doubtsabout the reliability of the temperature record Despite thisand other questions, a majority of climatologists feel that arisk of global warming exists, although there is much dis-agreement concerning the extent and timing (One of theuncertainties is the possibility that large amounts of meth-ane now locked in Arctic tundra and permafrost could berapidly released if warming reaches a critical point.) At the

1992 United Nations Conference on Environment and velopment, more than 150 countries signed the U.N Frame-work Convention on Climate Change, which pledges signa-tories to control emissions of greenhouse gases

De-In 1992 the Persian Gulf states of Qatar and the UnitedArab Emirates had the highest per capita emissions of car-bon dioxide—16.9 and 11.5 metric tons, respectively—whereas the U.S was in eighth highest place with 5.2 metrictons Overall, the U.S produced 23 percent of global emis-sions, western Europe 14 percent, the former communistcountries of eastern Europe 20 percent, and Japan 5 percent

Of the developing countries, China was the biggest utor in 1992 with 12 percent, followed by India with almost

contrib-4 percent Although emissions have more than tripled ing the past 40 years, they showed signs of leveling off inthe late 1980s and early 1990s —Rodger Doyle

dur-METRIC TONS PER CAPITA IN 1992 LESS THAN 1

SINGAPORE

B Y T H E N U M B E R S

Carbon Dioxide Emissions

Trang 15

is eased(again, as with the yew), but then

it can become hard to ensure that some

proceeds return Roger Kennedy, director

of the National Park Service, has

pro-posed that royalties from finds—such as

the bacterium Thermus aquaticus, which

was discovered in Yellowstone National

Park and used in the enormously

profit-able polymerase chain reaction—be used

to protect the parks

This idea is disputed by some

phar-maceutical companies and by other

ob-servers, who point out the differences

between property and intellectual

prop-erty In the case of T aquaticus, the

counterargument goes, scientists

dis-covered PCR—the technique is the

prod-uct of their effort and thought Thus,

their intellectual work and financial

in-vestment deserve to be protected Many

experts feel that the Biodiversity

Con-vention (which the U.S has still not

rati-fied) does not adequately protect patents

or intellectual property

At the same time that developing

coun-tries are demanding a share of the

royal-ties from drug discovery, many

biopros-pectors argue that the promise of such

revenue is overblown One profitable

drug is developed, after 10 or 15 years,

from some 10,000 to 100,000

substanc-es that are screened “The royaltisubstanc-es may

never come,” points out Ana Sittenfeld

of INBio, a Costa Rican organization

that supplies extracts to several

phar-maceutical firms, including Merck For

instance, the National Cancer Institute

(NCI) screened nearly 80,000 biological

materials between 1986 and 1991—

only one major lead has emerged so far

Small biotech companies have,

how-ever, discovered how to make money not

just from the end product—the drug—

but also from the steps that lead to it

Some rent out samples to

pharmaceuti-cal companies for screening; others do

the screening and provide leads to

sub-stances The industry assigns well-defined

trade values to each step: extracts sell

for $10 to $100, leads sell for $100 to

$1,000, and a drug candidate with

ani-mal toxicology data sells for $1,000 to

$10,000 “Those countries that had

ac-cess to this market information have

ne-gotiated the best deals,” Putterman notes

The most valuable benefit, Sittenfeld

states, is technological training INBio,

often cited as an example for future

Third World institutions, functions much

like a biotech company, with attendant

profits In contrast, Abegaz laments a

“failure to build capacity in Africa.”

Among the bioprospectors in Africa is

the NCI, which has been criticized forproviding minimal up-front benefitsand no guarantee of royalties

INBio puts 10 percent of its researchbudget into conservation and trains lo-cal parataxonomists, who might other-wise have been using the forests in non-sustainable ways The International Co-operative Biodiversity Groups Program,set up by three U.S agencies—the Na-tional Institutes of Health, the NationalScience Foundation and the Agency forInternational Development—also tries

to build local capacity while ing Joshua P Rosenthal, who heads theprogram for the NIH, comments thatsuch training helps local scientists inidentifying areas rich in biodiversity

bioprospect-A handful of other bioprospectorshave set up trust funds that promise re-turns if royalties ever start to flow Butensuring that biodiversity survives itsvalue to humanity remains a climb up aslippery slope — Madhusree Mukerjee This is the second in a two-part series

on profiting from biodiversity.

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Of all the diseases that afflict

humankind, none is more

prevalent than tooth rot By

the age of 17, almost 85 percent of

ado-lescents in the U.S have had multiple

cavities, according to a recent article in

the journal Public Health Reports

The basic reason for this pervasiveness

is that dentists often cannot detect the

onset of decay until it is too late But

re-searchers and dental professionals have

high hopes for an experimental

diag-nostic tool that, if it ever goes into

pro-duction, could detect problems while

there is still time to prevent cavities

Decay begins just under the tooth’s

surface, in the enamel coating Bacterial

fermentation of the carbohydrates from

food creates acids that cause the loss of

mineral in the enamel (which is about

90 percent mineral when healthy) Ifthis demineralization reaches the un-derlying dentine, the enamel eventuallycaves in, forming a cavity

If a dentist can catch demineralizationbefore it becomes too advanced, fluo-ride treatments can heal the lesion Butdentists seldom can “Decay has to beadvanced to be seen or felt,” explainsGeorge E White of the Tufts UniversitySchool of Dental Medicine The onlytools most dentists have are their eyes,the infamous metal pick—which theyuse to detect spots made fragile by dem-ineralization—and the x-ray machine

These methods do not work well cent studies have found that even withx-rays, dentists miss at least half of theseprecavity lesions Tooth enamel is quiteopaque to x-rays, so the demineralizedregions are often obscured by adjacenthealthy enamel

Re-Now members of a research groupfrom the universities of Dundee and of

St Andrews, both in Scotland, and theUniversity of Nijmegen in the Nether-lands say they have found a much bet-

ter approach They describe their

find-ings in a recent issue of Nature

Medi-cine Their technique, which measures

the electrical impedance of a tooth face to determine whether it contains ademineralized region, was 100 percentaccurate in trials on extracted teeth The method exploits the fact that de-mineralization opens up pores that fillwith a fluid that is much less electricallyresistant than enamel The technique isnot new But the Dundee team increasedaccuracy considerably by measuring im-pedance using alternating-current wave-forms over a broad spectrum—from onehertz to about 300 kilohertz

sur-The procedure took 10 to 15 minutes

to measure impedances separately onall four sides and the top surface of asingle tooth That time, however, could

be cut to seconds by more selective plication of the frequency bands used

ap-on each tooth, says Christopher Lap-ong-bottom, one of the Dundee researchers

Long-He and his colleagues are currentlyseeking funds to produce a version oftheir system that would be suitable forclinical use — Glenn Zorpette

News and Analysis

ELECTRIC SMILE-AID

There’s a new way

to stave off cavities

DENTISTRY

BIOLOGY

Environmentalists often call attention to the erosion of

Earth’s biodiversity Yet even the most knowledgeable of

them often has difficulty following such warnings with clear

statements about the value of what has been lost Now

ecolo-gists have demonstrated at least one benefit of biodiversity: a

multiplicity of species makes some lands more productive

G David Tilman and Johannes Knops of the University of

Min-nesota, along with David A Wedin of the University of Toronto,

recently published this report in Nature Their investigation

in-volved a set of 147 grassland plots; each measured three by

three meters square and

was planted with a

con-trolled mixture of grasses

(right) Using student labor

for the frequent weeding,

the researchers allowed

only one kind of grass to

grow on some squares,

whereas in others they

maintained many types In

some plots, 24 different

species

sprouted—seem-ingly a vast variety but still

only a mere fraction of the natural variation Wedin says native

prairies easily have 40 to 50 species

The point of the strangely quilted field was to determine how

the richness of species affected the land Charles Darwin long

ago reported that a mixture of different grasses can support

higher biological production than can a single type of plant

But according to biologist Peter Kareiva of the University of

Washington, no one quite knows which experiments Darwinhad in mind

Tilman and his co-workers demonstrated Darwin’s point

clear-ly by monitoring the effect of species richness on the peakstanding crop (as measured, for example, by the amount of aplot covered by grass) Plant cover expanded from 33 to 49 per-cent as the number of species rose from one to six Interest-ingly, with greater than six species, further productivity gainswere hard to see; the researchers could find no indications ofincreasing productivity on plots for which the number of grass

species surpassed 10

“So do these results tellthe policy maker to worryabout preserving the first

10 species of prairie plantbut not to bother once thatquota has been satisfied?”asked Kareiva in a com-mentary in Nature Clearly,more work would be neces-sary to gauge how a great-

er richness of species mightoffer other advantages,such as resilience to drought, predatory insects or disease ButTilman and his team are keen to address such questions Theyhave established a group of 342 plots, each 13 by 13 meterssquare “The bigger plots will be more valuable,” Wedin remarks.But new results showing the other values of biodiversity willperhaps take quite a bit more time As Tilman notes, “Handweeding 20 acres is a slow process.” —David Schneider

The More Species, the Merrier

Trang 17

Television Arrives

on the Internet

Someday soon, just about

every-thing will be networked

Televi-sion may well be next

Intercast-ing is a technology developed by Intel

that intertwines World Wide Web pages

with television broadcasts With it,

vid-eo producers can back up their real-time

broadcasts with all the resources of the

Internet So a sports fan could call up

batting averages to a window in the

screen of a baseball game News

pro-grams could provide reams of

back-ground analysis for those eager to look

beyond the limits of a 30-second spot

And advertisers could offer viewers the

chance to buy their product—or to get

more information about it

Station KGW in Portland, Ore.—the

local TV station to Intel’s Hillsboro

plant, which is taking the lead in

Inter-cast development—ran a successful

dem-onstration last year PC makers

Gate-way, Packard Bell and others promise a

full range of Intercast-equipped

com-puters over the course of 1996 The hope

is that the broadcasting will begin in

earnest as soon as the machines start

hitting the shops

And as it does, one of the easy

assump-tions made about the new media will be

shown to be hopelessly wrong New

me-dia do not replace old: they complement

them We won’t all be reading our

news-papers on-screen and watching

interac-tive TV on our PCs But the expanded

media of the Net will enrich print and

broadcast with their own unique

capa-bilities, and vice versa The process has

already begun, and Intercast may well

accelerate it

The technology is simple Television

signals contain pauses, called vertical

blanking intervals, to provide time for

the electron beam that creates the

pic-ture to scoot back up from the bottom

of the screen to the top In America,

those gaps are already used to transmit

data that create captions for the deaf; in

Europe, they transmit teletext

informa-tion Intercast takes up about half of

the remaining capacity, and it uses it to

transmit Web pages at about 96,000 bits

a second—about three times faster than

today’s quickest modem The Web

pag-es are stored on a hard disk on the

Inter-cast PC/ TV and displayed in a window

on the screen Nothing fancy is required

Many PCs already receive and displayvideo signals The only special elementneeded for Intercast is a $50 chip fordecoding the broadcast Web pages

The interesting stuff begins when theWeb pages hit the hard disk At thesimplest level, those pages can containbackground information about thebroadcast—which can be pretty dull But

if the PC/ TV is connected to the net, the pages can bring an interactivedimension to the broadcast Instead ofjust passively watching what’s beamed

Inter-to the screen, the viewer can follow thelinks from the Intercast Web pages tothe Internet Bingo: instant interactive

TV, using infrastructure and technologythat already exist

Want to know about the movie youare watching? An Intercast old-movieslink could connect you to a database offilm information containing everythingfrom biographies of the cast to copies

of the reviews the film received Want

to play along with a game show? Youcould pick an answer, or buy a vowel

Because Web pages can connect to puter programs or to people (via e-mail,say, or videoconferencing), the only lim-

com-it on the interactivcom-ity is the bandwidth

of the link from PC/ TV and the Net Inpractice, most people will have “fast”

modems, capable of transmitting about28,800 bits a second, fast enough fortext and simple (still) graphics But intheory, cable companies promise thisyear to start rolling out speedy modemsthat can transmit more than one million

bits a second, fast enough for tary video

rudimen-But if Intercast is to fulfill this tial, TV program makers will have toget smart about the ways in which newmedia can complement old There’s nopoint in simply doing slowly what canalready be done well via broadcasting—like shoveling out prepackaged infor-mation Three of the new media’s capa-bilities will prove crucial in making themarriage work:

poten-• Richness There is more tion on the Web than could be broad-cast over decades of television, let alone

informa-in a sinforma-ingle half-hour show So whereas

TV necessarily has to aim for the broadmiddle ground, the Web can cater to in-dividual whims and interests

• Interactivity The Net is a two-waychannel, allowing people to talk back

to the makers of TV programs and theirsubjects—and to participate in the pro-gram rather than just watch it

• Ubiquity Cyberspace is a sharedspace: viewers interact with one anoth-

er as well as program makers So theycan create true communities of interestand action—and perhaps resolve one ofthe basic dilemmas of new media versusold Although TV watchers all sharethe same experience, they can only sitback and watch But on the Net, peoplecan interact Intercast just might create

an interesting meeting ground that ters true community

fos-And if not Intercast, then somebodyelse will push forward with connectivi-

ty The possibilities of networking theworld have only begun to be explored.Many magazines and newspapers al-ready carry Web page addresses that willprovide more information about theirarticles—even Playboy bunnies now haveWeb pages

There is no reason why appliancescould not also be linked The oven could

be linked to recipes and cooking hints,preferably via a wireless link to a water-proof, handheld computer The officephotocopier could hook up both to themaker’s repair service and to an on-linemanual and help system Anythingyou’ve ever kicked, cursed or switchedoff just for being so determinedly andinanimately stupid could be improved

by bringing more information to it—andit’s only a connection away After all, ifthe Net can make television smart, justthink what it could do for a vacuumcleaner —John Browning in London

News and Analysis

CYBER VIEW

WATCHING PC/TV allows viewers to surf the Internet simul- taneously Here Ron Perkes of NetTV demonstrates the WorldVision system.

Trang 18

Several hundred tons of

plutoni-um, enriched uranium and other

highly radioactive materials have

been produced within the U.S over the

past two decades For every ounce

creat-ed, transported or sold, Department of

Energy officials entered a record into a

database The tracking system ensures

that no weapons-grade nuclear

materi-als are stolen or misplaced and provides

evidence that the U.S is complying

with international treaties But in 1993

the software, written 20 years ago for

an obsolete mainframe, had become

im-practical to maintain, so the DOEordered

a replacement

Because of the importance of the

sys-tem, Congress asked the General counting Office (GAO) to check up onthe project a year later The GAO’s reportwas disturbing It warned that the DOE’scontractor had started programmingwithout adequately analyzing whetherthe new design would work as well asalternatives, meet users’ needs or evensave money Despite the GAO’s admoni-tion, construction continued

Ac-Last fall the GAOissued a follow-upreview raising more serious concerns

The contractors, it found, could provide

no specifications, no test results, no statusreports The DOEhad no way of know-ing whether the project was on track

Agency managers could not even

esti-mate the size of the new system theless, in September the DOEswitchedoff the old tracking system and turned

Never-on the new Never-one without ever requiringthat the software pass a final test dem-onstrating that all its reports are accu-rate GAOreviewers have recommendedcanceling the project, warning that “thehistory of software development is lit-tered with systems that failed undersimilar circumstances.”

Indeed, in the history of federal ware procurement, expensive, time-con-suming failures are the rule The costs

soft-to taxpayers are threefold First are rect losses from investments in technol-ogy that is never used, such as a Federal

di-News and Analysis

SYSTEMATIC ERRORS

A new law aims to prevent software

meltdown in federal agencies

Trang 19

Bureau of Investigation

fingerprint-scan-ning system ordered in 1993 Already

late and more than 50 percent over

bud-get, the system uses technology so

out-dated that police advisers recently

vot-ed to reject and rebid the contract

Secondary costs go to pay salaries and

maintenance fees to keep obsolete

sys-tems running while modernization

proj-ects drag on The National Weather

Ser-vice’s upgrade of its observation and

forecasting systems, for example, has

slipped five years and doubled in cost

be-cause of poor design and management

Most painful, however, are the lost

savings that could have been realized

had agencies applied technology

effec-tively While the Internal Revenue

Ser-vice has frittered eight years and $2.5

billion trying, with little success, to

mod-ernize its systems in order to combat

fraud and noncompliance, an estimated

$70 billion in uncollected taxes has

slipped through the government’s fingers

No one knows what return executive

agencies can expect from the $26.5

bil-lion they plan to spend on information

technology in 1996 But many industry

experts are certain that it is lower than

it ought to be One major reason, an

outdated law known as the Brooks Act,

vanished in February, when President

Bill Clinton signed a bill that radically

reorganizes the way federal agencies

purchase large software systems

The 1965 Brooks Act funneled nearly

all computer purchases through the

General Services Administration (GSA)

and forced agencies to pick contractors

through a lengthy competition The idea

was to ensure that the government paid

the lowest price for expensive

main-frames But as large machines yielded to

the market for personal computers, the

law became a costly anachronism

The legislation that repeals the Brooks

Act will require each federal agency to

appoint a chief information officer

(CIO) Although agencies will no longer

need the GSA’s (typically rubber-stamped)

permission to buy information

technol-ogy, they will have to report on the cost,

status and success of their projects to

the Office of Management and Budget

(OMB) The OMBwill have the

authori-ty to kill runaway systems by

withhold-ing their fundwithhold-ing—and the duty to send

an annual report to Congress

compar-ing the performance of the agencies

In place of the Brooks Act’s intricate

rules is a new set of detailed directions

Big systems must be split into small

in-dependent chunks so that later sections

can incorporate newer technology ments are supposed to be finished with-

Seg-in 18 months—faster than most currentprojects Perhaps the law’s most ambi-tious provision insists that agencies an-

alyze and redesign operations before

in-vesting in systems to automate them

Senator William Cohen of Maine, whosponsored the legislation, maintains that

it could save up to $175 billion over fiveyears Industry veterans suggest that esti-mate may be wildly optimistic, althoughthey generally agree with Larry E Druf-fel, head of the Software Engineering In-stitute, that “repeal of the Brooks Act has

to be positive.” Appointing CIOs, ting projects into pieces and enforcingrisk management could produce a morelogical approach, he says But Druffelwarns that “these components could alsoproduce a bureaucratic system in whichthe CIO becomes a bottleneck, securityconcerns inhibit the use of commercialproducts, and increments are built with-out any unifying framework, so thatnothing works with anything else.”

split-Richard A DeMillo, former head ofthe Software Engineering Research Con-sortium, points out that the law “recy-cles old ideas that have always soundedgood but haven’t been followed by con-tractors.” Indeed, the act gives agencies

no new leverage to deal with firms thatdeliver poor work, fall behind schedule

or raise their cost estimates midstream

If Congress has neglected oversight inthe past, “this goes to the other extreme,

of micromanagement,” complains PaulStrassmann, former CIO for Xerox,Kraft and General Foods “The funda-mental flaw here is that [Congress] pre-scribes inputs yet has very little interest

in results.” Congress, he suggests, shoulddemand reductions in overall agencycosts, not in the price of technology

“Treating each systems acquisition as

a separate [technological] solution,”

Strassmann testified in a Senate ing, “has resulted in thousands of unin-tegrated, hard-to-maintain, impossible-to-manage, contractor-dependent is-lands of automation.” Because the law

hear-“does not articulate what to do withwhat is already in place and what hap-pens after new systems are installed,”

Strassmann warns, “this act may ceed in eliminating much of the existingregulatory chaos of acquisition only tobecome saddled with a more costlychaos of operations.”

suc-—W Wayt Gibbs in San Francisco This is the second in a continuing series on computing and government.

ON SALE MAY 28

Also in June

Semiconductor Subsidies Can Yucca Mountain Safely Store Nuclear Waste? Controlling Computers with Biological Signals

THE ARTIST WHO BROUGHT DINOSAURS BACK TO LIFE

by Gregory Paul

OLYMPIC SPORTS TRAINING

Trang 20

The failings of conventional

flat-panel display technology are

familiar to anyone who has

used—or priced—laptop computers

In-expensive models are limited to shades

of gray or dim colors More advanced

versions capable of bright,

fast-chang-ing hues carry dizzyfast-chang-ing price tags And

all liquid-crystal screens suffer from a

voracious appetite for power, sucking

batteries dry within a few hours

Researchers at the Liquid Crystal

In-stitute of Kent State University have

re-cently demonstrated a new kind of

in-expensive liquid-crystal display (LCD)

that can produce clearer images using

much less energy Commercial

produc-tion of a high-resoluproduc-tion gray-scale

ver-sion has already begun at Kent Display

Systems The researchers are now

engi-neering a similar color device

The displays do more with less

be-cause they affect light in a different way

than conventional LCDs do A

stan-dard liquid-crystal panel filters the light

both going in and coming out Dots, or

pixels, of liquid crystal inside the panel

naturally twist the light so that it can

pass through the second filter But when

a pixel is turned on, it untwists, and the

dot goes dark

Unfortunate-ly, such polarized filters cutthe light going in by half;

changing bright pixels intocolored ones requires yet an-other filter LCDs are conse-quently too dim to use ascomputer displays unless lit

by a lamp from behind Andlamps devour power

Liang-Chy Chien and hiscolleagues got around thisproblem using a so-calledcholesteric liquid-crystal ma-terial Rather than twistinglight, this material breaks in-coming rays into two parts

One ray is reflected; the

oth-er is transmitted Electrifyingthe chemical turns it clear Because cho-lesteric LCDs reflect light without theneed for polarizing filters, they can be

as bright and legible in ambient light asconventional LCDs are when backlit

Early cholesteric LCDs were limited

to single colors, but Chien found that if

he added small amounts of a second terial, he could tune the color to any-thing from deep red to brilliant blue byshining various amounts of bright ultra-violet light on the panel Mixing in a bit

ma-of polymer then locks in the chosen

col-or The engineers are now adaptingmasks such as those used to etch micro-scopic patterns onto computer chips tocreate millions of red, blue and greenpixels on a cholesteric LCD panel

At present, cholesteric LCDs are about

20 percent more expensive than tional “passive matrix” displays, but

conven-their effects are worth far more Pixels

in the new displays stay on once theyare turned on, eliminating the need toredraw the display several times eachsecond, thus saving power These panelsshould run more than 10 times longer

on batteries than present displays can.The stability also allows pixels to bemuch smaller—one prototype boasts

200 dots per inch—and it eliminates theflicker that makes laptop screens weari-some to read But the biggest advantage

of the new LCDs is that they do not quire the “active matrix” electronics thattriple the price of conventional panels

re-in order to mare-intare-in high contrast andresolution A wide range of electronicsmakers, including IBM, Sony and Toshi-

ba, have reportedly expressed interest

in licensing the technology

—W Wayt Gibbs in San Francisco

News and Analysis

ON PERMANENT

DISPLAYS

Low-power, low-cost liquid

crystals move to market

Migrating Metaphors The terminology

of computer networks is gradually

mak-ing its way into the general lexicon For

example, low bandwidth, as in the

dis-paraging “He has very low bandwidth” or

“What a low bandwidth group,” is a

put-down of mental capacity Bookmark, as

in the approving “I bookmarked them,”

is a verb for people one might wish to

telephone or e-mail in the future, perhaps

after a successful business presentation

And mostly digital, as in “I’m mostly

digi-tal,” is said of the reading habits of those

who prefer e-mail, news groups, chat

lines and Web sites to books

Licensed to CyberNotarize The

Ameri-can Bar Association is working on a new

legal specialization—the CyberNotary

Those licensed in the field will cate and certify commercial electronicdocuments destined for abroad, wherelegal procedures and content differ sub-stantially and where transactions aremade still trickier by the advent of elec-tronic commerce CyberNotaries will beexpert not only in international law butalso in digital-signature technology, at-testing to electronic identities on cor-porate share transfers and establishingthat parties of the first part truly pos-sess the public keys that they purport topossess The ABA CyberNotary ProjectWorld Wide Web page is at http://www

authenti-intermarket.com/ecl

Carpet Tunnel Syndrome? During the

1980s, bemused operators on computerhelp-lines fielded calls from people un-able to work their mouse buttons Itturned out that new users were placingthe devices below their desks and trying

to operate them by foot Nowadays,though, a tapping foot may be just right.Hoping to eliminate the hazards of carpaltunnel syndrome, manufacturers have be-gun introducing a foot-pedal mouse thatsits on the floor, freeing hands In onetwo-pedal model, users tap the left pedal

to click They rotate their foot on theright pedal to direct the cursor, pressingdown for speed —Anne Eisenberg(aeisenb@duke.poly.edu)

Trang 21

During the past two years, a

dozen varieties of cotton,

squash, soybeans, potatoes

and tomatoes created by gene splicing

have been approved for sale in the U.S

The added genes confer traits ranging

from longer shelf life to pest resistance

The plants seem safe, but environmental

watchdog groups fear that the spliced

genes might spread into the crops’ wild

relatives In such hosts, the genes might

be less benign—and harder to control

Researchers have long known that

transgenic plants can form sterile

hy-brids with wild relatives Now

research-ers in Denmark have shown that these

hybrids can be fertile and can transmit

a genetically engineered trait to

subse-quent generations in field conditions

Health concerns have also emerged: a

report in the New England Journal of

Medicine indicates that a gene taken

from Brazil nuts and engineered into

soybeans made the beans allergenic

The Danish researchers, Thomas R

Mikkelsen and his colleagues at the

Risø National Laboratory in Roskilde,

crossed oilseed rape (also known as

ca-nola) that had genetically engineered

re-sistance to a common herbicide,

glufos-inate, with a weedy relative of the crop,

Brassica campestris They then bred the

hybrids with wild B campestris to

cre-ate glufosincre-ate-resistant plants

Further-more, the plants transmitted glufosinate

resistance to the next generation “I have

been waiting for something like this to

happen,” comments Norman C

Ell-strand of the University of California at

Riverside “This demonstrates that you

can get expression of a novel gene in a

weed plant, and it has high fitness.”

Resistance to herbicides has been a

popular trait for genetic engineering,

because the plant developers can sell

the seeds with the promise that the crop

will not be harmed by use of the proper

herbicide Plant Genetic Systems in

Bel-gium has obtained marketing approval

in Britain for glufosinate-resistant

oil-seed rape, and Monsanto sells soybeans

that are resistant to the herbicide

gly-phosate But if weeds acquire resistance

genes from the crop, the commercial vantage will quickly evaporate

ad-That scenario is plausible only if thereare weedy relatives in the area where thecrop is grown Gene spread from soy-beans in North America seems unlikely,because the crop has no wild relatives

But soybeans in Asia do have such bors, and canola and squash have nu-merous wild relatives in North America

neigh-Genes for herbicide resistance bly will not get far outside of a con-trolled agricultural setting, because theyoffer no advantage where the herbicide

proba-is not used Genes for pest resproba-istance are

a different matter Even seemingly nocuous traits such as altered oil com-position might give a weed a boost ifthe traits were to spread The Union of

in-Concerned Scientists has called for moreresearch on a virus-resistant crooknecksquash marketed by Asgrow and a mod-ified canola, sold by Calgene, that pro-duces seeds with oil rich in lauric acid

Beyond the threat of the spread of sistance lies the worry that other harm-ful attributes could be transferred be-tween transgenic crops Scientists havelong been aware, for instance, that if aplant is given new genes, it produces newproteins, and some proteins can cause

re-life-threatening allergic reactions in ple This possibility just became realityfor Pioneer Hi-Bred International, whichhad engineered a Brazil-nut gene intosoybeans intended for animal feed in or-der to provide extra methionine to sup-plement the animals’ diet The companycalled off the project before any beanswere sold, after tests showed that theBrazil-nut protein it had used caused al-lergic reactions when extracts of thesoybeans were tested on people.Despite the discovery that transgenescan spread by hybridization into weedyrelatives of crops, the U.S Department

peo-of Agriculture has proposed ing the procedure companies follow toget approval for field tests of geneticallyengineered crops “Sex does happen, and

streamlin-we know about it,” says Arnold Foudin

of the Animal and Plant Health tion Service “The question is: Does itpose risk elements that have not tradi-tionally existed? The answer is, not re-ally.” Others are less sanguine “I don’tthink there should be a class of genes orspecies that we assume are never going

Inspec-to cause problems,” says C Randal der of the University of Illinois “The

—Tim Beardsley in Washington, D.C.

News and Analysis Scientific American May 1996 33

ADVANTAGE: NATURE

Could escaped genes

from bioengineered crops give

weeds a crucial boost?

fessor reports In February, poor and graduate student MehranMojarrad demonstrated a platinum-coated ion-exchange membranethat runs on electricity instead of achemical solution Mojarrad hascreated sheets of the plastic mate-rial that curl when electrodes arecharged on either side So far theresearchers have constructed onlydemonstration toys from the mate-rial: a boat propelled by a wavingfin of polymer, and a flapping ma-chine that they believe may yet getoff the ground But more practicaluses for a cheap, noiseless andhighly efficient artificial muscle areprobably not far off

Shahin-—W Wayt Gibbs in San Francisco

MATERIALS

Trang 22

Your computer system is down,

and you don’t know why

Wouldn’t it be convenient if

the manufacturer could diagnose and

fix the problem over the telephone lines

or send you the needed spare even before

your system bombed? Such a scheme

could be in place within a year, at least

for industrial manufacturing equipment

The idea is to have a kind of data

re-corder within a piece of equipment that

would transmit information on

operat-ing conditions to the original

manufac-turer The firm can use the data to

dis-patch a replacement or even send

com-mands that restart the device

That is the hope of Richard S Post,

head of Applied Science and Technology

(ASTeX), a company in Woburn, Mass.,

that supplies components, such as

plas-ma sources and microwave power

gen-erators, for semiconductor

manufactur-ing Currently semiconductor-making

equipment remains down about 15 cent of the time for maintenance Toconstruct more durable machinery, Postsays, one needs to know the conditionsunder which the machine failed, such asthe temperature it reached or the voltage

per-it drew But that kind of information israrely available “You just get the com-ponent back in a bag with a note saying

it doesn’t work,” Post complains itoring over the Internet might also ob-viate the need for a return shipment: acommand could be sent that simply re-sets the device or that confirms it hasactually malfunctioned

Mon-The idea of using networks to monitor

a piece of equipment is not new phone companies already employ a sim-ilar strategy, notes Ralph Wyndrum ofAT&T Bell Laboratories They routinelytest their lines and reroute calls aroundglitches before any disruption occurs

Tele-The value of the Internet, however, isits economical utility: it is virtually freeand has global reach Moreover, nohardware needs to be invented Micro-processors are often embedded in equip-ment (for every one personal computer,there are 10 home and business machineswith a processor chip), and many ofthese chips can do diagnostic tests

And software exists to connect these

“intelligent” devices For the past year,Novell in Orem, Utah, has been toutingsoftware called NEST, which links of-fice machines so that, say, a single faxtransmission can be dispersed to severallocales More important, it can collectreal-time data about the devices andgenerate statistics on their use At theend of March, Novell began selling aversion that is compatible with the In-ternet With the hardware and softwareavailable, the principle of remote moni-toring over the Internet can be demon-strated in a matter of weeks, claims Post,who has only just begun floating theidea to colleagues and customers Realsystems could be had in a year

Unfortunately, the ability to determinewhat a device is doing also suggests thatinformation flow can be reversed, mak-ing sabotage a possibility And sendingproprietary operating data across theInternet makes it game for industrial es-pionage Such security issues, though,are not that different from dealing withcredit-card and other sensitive transac-tions over the Internet, Post remarks

He thinks that even a 5 percent increase

in productivity would be worth the tempt: “We just have to decide whatkinds of things to include in the nextgeneration of devices.” —Philip Yam

at-News and Analysis

REMOTE REPAIR

Internet technology may allow

equipment to be fixed from afar

INFORMATION TECHNOLOGY

From the Red Baron’s Fokker to the stealthy,

state-of-the-art F-22, fighter aircraft have always sported a tail But

for rear fins, the end may be in sight

On March 19 the National Aeronautics and Space

Adminis-tration unveiled the X-36—the first high-performance jet with

no tail at all Remotely controlled and powered by a

cruise-mis-sile engine, the 5.4-meter-long, 600-kilogram

scale model represents “a major breakthrough

in our ability to couple aerodynamic surfaces with

thrust vectoring and flight-control laws to achieve

truly tailless, agile flight,” says Larry

Birckel-baw, who led the X-36 project at the NASAAmes

Research Center at Moffett Field, Calif

Why go tailless? Because it can make a jet

much more stealthy, Birckelbaw notes And

that’s not all: a finless posterior can

significant-ly improve performance As much as 30 or 40

percent of the drag on a conventional jet fighter

comes from the tail, Birckelbaw estimates In a

typical design, though, the tail is crucial for

aerodynamic stability and maneuverability The

X-36 does without one by making extensive use

of thrust vectoring—the ability to change the

di-rection of the engine’s thrust The trick,

Birckel-baw explains, was designing the X-36’s

aerody-namics so that the airplane would not spin out of control if thevectoring capability failed

If Birckelbaw has his way, the diminutive X-36 will changethe shape of high-performance airplanes “I’m very hopefulthat these technologies will make a major impact on fighters

in the future,” he says —Glenn Zorpette

ENGINEERING

Winging It

Trang 23

A Natural History

of Fleas and Butterflies

The house at Ashton Wold is

wild, outside and in Although

it is muddy midwinter and the

twisting branches and vines are bare, it

is clear that the garden is a lush, unruly

tangle in the spring and summer, that

things are just let be In the large living

room, too, things are everywhere: an

imposing pine tree hung only with its

own cones, a sideboard with cakes and

coffee, walls of bookshelves as well as

long tables piled high with books—about

fleas, birds in Israel, mother-daughter

re-lations, Beatrix Potter’s botanical

draw-ings, and memory There are pictures of

birds and butterflies and photographs

of the children and grandchildren and

one of Walter Rothschild on the back

of his giant tortoise Rotumah, a stuffed

owl, vases of yellow flowers and star

lilies, many small jars of seeds, two ing dogs, myriad couches

bark-And Miriam Rothschild, whose terests, accomplishments and moodsare as diverse as her sitting room Sheeven has another last name, Lane, thatshe uses when it suits her—sometimeswhen callers ask if they are speaking toMiriam Rothschild, she will answer, “Itdepends Who are you?” (“Lane” waswhat the British Commandos dubbedher husband during World War II, be-cause his Hungarian name sounded sodecidedly un-English.) It is the name

in-“Rothschild,” however, that appears on

her some 350 papers aboutentomology, neurophysiol-ogy, chemistry and zoologyand on the roster of the Roy-

al Society

And it is as a Rothschildthat she is known for her doz-

en books, much of her vation work, her advocacy forthe better treatment of ani-mals, her gallery devoted tothe artwork of schizophren-ics, her political activism onbehalf of homosexuals, andall the other hundreds ofthings she has done in hernearly 90 years “I am a tilter

conser-at windmills,” Rothschild serts from her wheelchair,where she is temporarilystuck because of an injury

as-No matter that the furniturehas been rearranged to ac-commodate the large Christ-mas tree, Rothschild takesthe same path as ever to theever ringing telephone, push-ing chairs and small tablesout of her way “I alwayshave had some cause or oth-

er which I really get terriblysteamed up about.”

Her expansive interests, herenergy and her activism are

in keeping with her lineage The schild family—famous for banking andpolitics—has produced astounding nat-uralists: Walter, whose collections in-cluded 2.25 million butterflies, 30,000birds and 300,000 beetles; and Charles,Miriam’s father, who assembled themost comprehensive flea inventory inthe world Rothschild’s first memoriesare of being obsessed with nature andwith collecting specimens Her parents

Roth-believed that a formal education would

be too stifling, so she was free to pursueher interests and to read widely At 17she decided to take some courses

“Right in the beginning of my sity life, if you call it that, I tried to taketwo degrees at once: English literatureand one in zoology But it became im-possible You could never get the lec-tures synchronized You always wanted

univer-to hear somebody talk on Ruskin, and

at the same time you had to dissect theentrails of a sea urchin It was hopeless.”Rothschild ultimately chose marine bi-ology because of a field trip to Plymouthand a chance meeting with naturalist G

C Robson “He offered me the world if

I would stick with his marine snails,” sherecalls—and he packed her off to Italy

to do so, as the winner of an all-paid sition “I went home to my mother andsaid, ‘You will be very pleased to hearthat I have been awarded the LondonUniversity Table in Naples.’ I didn’t tellher I was the only applicant I thought itwas high time she thought I was clever,instead of being the stupid one in thefamily.”

po-There were no such snails, but schild had a wonderful time: “My trou-ble at Naples was that I merely went intoeverything because it was all so fascinat-ing.” She returned to England, working

Roth-on snail-borne parasites for seven years,until her lab at Plymouth was bombed

in 1940 Rothschild has written aboutthe sudden destruction as horrible butalso liberating: “Without realizing it Ihad gradually become an appendage of

my trematode life cycles.” She then didsome wartime work “I made a foodfor chickens out of seaweed, and I wasasked, ‘Do you think this is a success?’And I said, ‘I don’t know It gives methe hiccups.’ ” Rothschild stops and lis-tens as the dogs begin to bark, high-pitched and persistent; when they calmdown, she continues

Rothschild was asked in the early1940s to join Enigma (or Ultra, a proj-ect to decode German communications)with, oddly, a bevy of marine biologists

“There was the champion chess player

of Ireland, and there were all these topmathematicians But on the whole themarine biologists came out way ahead

It was very funny.” The work was rying, she says tersely “Look, I can sum

wor-up my views on Enigma: we didn’t winthe war, but we shortened it.”

News and Analysis

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She left Enigma to marry her husband

and to work on an agricultural council,

studying wood pigeons She discovered

that the birds carried bovine

tuberculo-sis “People said there was a different

breed of wood pigeon, a different strain,

that came to this country in the winter,

which had darker plumage.” To her, the

coloring suggested addisonism, which

people have when their adrenal glands

are infected with TB “I went to the meat

market, and I dissected an awful lot of

pigeons there And then I found this TB

in the adrenals.” (She was not allowed to

publish her results, because, she confides,

“it gave the enemy information, which

I thought was remarkably funny.”)

Rothschild does not characterize her

hunch about the TB—or any of her

re-markable hunches—as

intuitive “I think if you

had to describe any

tal-ent I might have, it is

that I am a good

observ-er And that means that

you don’t only notice things, but you

think about what you have noticed.”

After the war, at the age of 44, she

wrote her first book, Fleas, Flukes and

Cuckoos, about parasites, and then

con-centrated on the family fetish: fleas

Charles, who, among other things,

iden-tified the flea that carried the plague,

had housed his tiny millions at the

Nat-ural History Museum in London, but

they had yet to be catalogued Being the

mother of six posed no challenge to

Rothschild “I guess roughly I gave up

10 years to the children And I have

al-ways been quite honest about this: I

much prefer children to the fleas It was

not a sacrifice to me at all And I never

really believed a word of these women

who said they could not give up their

careers; it is obvious the children are

more interesting than the careers.”

She does admit that she is a chronic

insomniac “One thing that made it easy

was you could look after the children in

the daytime, and you could do your

mor-phology and your microscopy at night.”

She apparently also dispenses with

time-consuming chores like choosing clothes

by wearing one outfit that she designed

and had made up in various fabrics

Working with a collaborator for 20

years, Rothschild catalogued and

inves-tigated the peculiarities of fleas: “I

dis-covered, just by accident, that if you

knew the histology of the flea you could

pretty much know the histology of any

other insect.” She points to some

draw-ings “Look at their lovely mouthparts

They have got such beautiful parts, fleas Really, they have.” Roth-schild also discovered how fleas jump

mouth-so well They have a ball of resilin tween their back legs; this elasticlike sub-stance allows them to jump from bend-

be-ed knee off the ground at more than

140 times the force of gravity Some dothis 30,000 times without stopping

In the midst of studying rabbit population in Australia, Rothschild dis-covered the first example of a parasiterelying on its host’s hormones “I wasable to show that the flea has turnedover the control of its breeding cycle tothe rabbit Its ovaries only mature un-der the influence of the pregnant rab-bit’s hormones,” she explains in crisp,clear manner “During copulation be-

over-tween adult rabbits, thefleas all move off the buckonto the doe—she seems

to attract them at thatstage Then, when she be-comes pregnant and be-gins to mature her baby, so to speak, thefleas gradually go through her cycle

And their ovaries begin to develop Bythe time she is ready to give birth, thefleas respond to this and instead of re-maining attached to the rabbit ear, asthey do normally, they break loose, rundown the rabbit’s nose and drop off onthe babies just as they are born Therethey receive another set of hormonesthat enables them to copulate.” (Roth-schild has said that this synchronicitymay explain why women are more of-ten bitten by fleas than men are.)She stopped her work on hormoneswhen her collaborator at the University

of Oxford, Geoffrey W Harris, died

“Somehow the gilt was off the bread, you know.” Rothschild attrib-utes much of her luck to collaborators

ginger-“Without the enthusiasm, I mean, youknow I am an amateur, I have no de-grees.” With Nobel laureate TadeusReichstein, Rothschild determined thatthe poison of monarch butterflies comesfrom their diet of milkweed She contin-ues to study butterflies—her first love,she says, and the subject of her most

recent book, Butterfly Cooing like a

Dove—as well as toxins and chemicalsignaling in insects and plants

Plants, in fact, are a current obsession

Rothschild is revisiting 180 of 280 sites

in the British Isles that her father scribed in 1912 as areas vital to preserve

de-She hopes to determine which forms ofland management failed She has alsodevoted 150 acres of her estate to rare

wildflowers and is selling the seeds so

as to preserve genetic diversity

General-ly, population growth and the tion of the natural world depress her.But “there is only one single, slight goodthing And that is that a different class ofperson now is interested I hate the word

destruc-‘lower classes,’ it is a horrible word, but

it is true,” she says There are “more educated people who have become in-terested in the environment.”

un-Her other concerns of the moment arememory (how certain chemicals triggerrecall) and the plight of animals Roth-schild argues compellingly for animalconsciousness and is trying to reformhow farm animals are housed andslaughtered in England She is remorse-ful about some of the experiments sheconducted in the past “People should betaught when they are young that they

have to consider the value of the

exper-iment before they start in on it It is solutely not enough to be interested Butyou get so carried away with interestthat you lose all sense of proportion.”Further, Rothschild is studying telep-athy in several dogs and cats that ap-pear to be able to tell when their own-ers are returning from a trip or are tele-phoning, even though no one else in thehousehold knows of these events Shehas put out ads (“Anyone whose dog orcat anticipates their return, please com-municate”) and is trying to design ex-periments to test her theory “There arequite a few funny things about dogs andtelepathy,” Rothschild remarks and re-counts how early one morning she wasawakened in London, far from home, byher dog barking She called her staff atAshton Wold and discovered the dog hadbeen barking for a while “Probably co-incidence, but now I feel as though Ineed to look into it.”

ab-And then there is the paper on birds she needs to look into, as well aslost papers of her father’s that have justbeen found and the meadow of Biblicalflowers she would like to create and thebook she is writing about Proust andthe weather “There comes a momentwhen counting the bristles on fleas be-comes a bore,” Rothschild says, explain-ing why she has always veered off into

lady-“corny” writing But then art and scienceare not really so far apart “My greatthing is that I believe the two are verysimilar and should go together,” she says

“You see, I am an amateur, not a sional zoologist Because if I was one,life would have made me specialize moreseverely.” —Marguerite Holloway

profes-News and Analysis

“I am a tilter

at windmills.”

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Finally, the terrible bloodshed in

Rwanda had come to an end

Alphon-sine and her family were returning to

their house when Alphonsine stepped

on an unseen mine At the hospital in

Kigali, run by the surgical team of the

relief organization EMERGENCY, I and

other physicians did what we could to

repair the damage The explosion had

smashed Alphonsine’s legs and fractured

her left forearm We had to amputate

both legs above the knee Her sister

sus-tained a penetrating brain injury from a

metallic fragment; she never regained

consciousness and died six hours after

surgery Their father, who had been

me-ters away from the two girls, had only

multiple small wounds in his chest.

As a surgeon for EMERGENCY, I

have treated many children such as Alphonsine and hersister—victims of a new kind of war

The great majority of modern conflictsare now internal rather than interna-tional: they are civil wars, struggles forindependence, ethnic and racial “cleans-ings,” terrorist campaigns Today armies

of irregulars without uniforms

routine-ly fight with devastating weapons in themidst of crowded areas Many armedgroups deliberately mix with the popu-lation to avoid identification Sometimesthey actually use civilians as shields

Quite often, targeting and terrorizinglarge civilian groups are part of anarmy’s primary military strategy

Accordingly, civilians have ingly become victims of war DuringWorld War I, they represented only 15percent of all fatalities, but by the end

increas-of World War II the percentage had

ris-en to 65 percris-ent, including Holocaustcasualties In today’s hostilities, morethan 90 percent of all of those injuredare civilians Numerous research insti-tutes, among them the Stockholm Inter-national Peace Research Institute andthe International Peace Research Insti-tute in Oslo, and humanitarian organi-zations involved in victim assistancehave confirmed these figures

One of the most dramatic aspects ofthis catastrophic change is the ever morewidespread use of inhumane weapons

The Horror of Land Mines

Land mines kill or maim more than 15,000 people each year

Most victims are innocent civilians Many are children

Still, mines are planted by the thousands every day

by Gino Strada

Trang 26

such as antipersonnel mines They

char-acteristically pose an indiscriminate and

persistent threat Land mines do not

dis-tinguish the foot of a combatant from

that of a playing child Land mines do

not recognize cease-fires or peace

agree-ments And once laid, they can maim or

kill for many decades after any hostilities

have ended For this reason, the

anti-personnel mine has been referred to as

“a weapon of mass destruction in slow

motion.”

Mine Pollution

Mines have been used in various

guises since the beginning of the

century, but military philosophy has

evolved over the years to make more

cunning use of them They are no longer

seen simply as weapons for denying an

enemy certain lands, or for channeling

an enemy’s troop movements, or for

protecting key installations Instead they

are now often laid to deprive a local

pop-ulation access to water sources, wood,

fuel, pathways and even burial grounds

In many countries, in fact, helicopters,

artillery and other remote means have

been used to scatter mines randomly

over villages or agricultural land as

de-liberate acts of terrorism against the

civilian population

In technical terms, an antipersonnel

mine (also known as an AP mine) can

be defined as a device designed to kill

or maim the person who triggers it (Incontrast, antitank mines, usually calledATMs, are specifically designed for blow-ing up tanks and vehicles They explodeonly when compressed by somethingweighing hundreds of kilograms.) APmines are generally rather small in diam-eter, frequently less than 10 centimetersacross, and difficult to detect In somecases, the color and shape of the minehelp to camouflage it so that it becomesvirtually invisible at a glance

A land mine is activated when the tim triggers the firing mechanism, usu-ally by applying direct pressure to themine itself or by putting tension on atrip wire That action sets off the deto-nator, which in turn ignites the boostercharge, a small amount of high-qualityexplosive The detonation of the boostercharge detonates the land mine’s maincharge, completing the explosive chain

vic-In recent years, mine technology hasevolved significantly The development

of plastic mines, as well as those taining a minimum amount of metal,

con-has made these weapons cheaper, morereliable, more durable and harder to de-tect and dismantle In addition, remotedeployment systems (such as helicop-ters) have made it possible to deliverthousands of mines to a broad territorywithin just a few minutes Laying mines

in this way also makes it impossible torecord exactly where they land, so re-covering them is all the more difficult.Unfortunately, land-mine technology

is quite simple and its price very low—

most weapons cost in the range of $3 to

$15 As a result, they have been ably manufactured and sold by a risingnumber of countries in past years, in-cluding many in the developing world.Approximately 50 nations have pro-duced and exported antipersonnel mines,and at least 350 models are currentlyavailable, not only to official armies butessentially to all fighting groups andarmed factions worldwide

profit-The number of unexploded mines inplace around the globe is not known.According to several sources (includingthe United Nations, the U.S State De-partment and various humanitarian EMERGENCY ARCHIVE

SMALL SB-33 MINE, shown at its actual size below, blends with these stones so well that it becomes virtually invisible When a person steps on such a blast mine, the resulting explosion typically blows off a foot or leg Many antipersonnel mines are currently made in colors and shapes that help to camouflage them once laid.

Trang 27

agencies), at least 100 million are now

scattered across 64 countries Because

neither manufacturers nor users

typical-ly keep records, though, these figures

very likely underestimate the real

situa-tion Whatever the case, a significant

portion of the world undeniably suffers

from what might be considered

“land-mine pollution.”

The agencies offering victim assistance

or operations to clear mines estimate

that during the past two decades these

weapons have killed or maimed

approx-imately 15,000 people each year Of

these victims, about 80 percent were

civilians In fact, the actual number is

probably even higher given that many

accidents occur in remote areas without

medical facilities and so are not

docu-mented In a mined area, many

every-day activities—gathering wood or food,

drawing water, farming, playing,

tend-ing livestock—become highly risky I

have personally treated 1,950 people

in-jured by mines; of them, 93 percent were

civilians, and 29 percent were children

younger than the age of 14

The Damage Mines Inflict

Practically speaking, antipersonnel

mines can be divided into two large

groups: blast mines and fragmentation

mines Blast mines usually respond to

pressure—for example, from a

descend-ing foot on a sensitive plate The injuries

to the body from blast mines are directconsequences of the explosion itself Incontrast, fragmentation mines are usu-ally activated by trip wires When theyexplode, a large number of metallic frag-ments fly outward for a considerable dis-tance These fragments are either con-tained inside the mine or result fromthe rupture of its segmented outer case

The type of mine, the specifics of itsoperation, its position on the ground,the position of the victim and the char-acteristics of the environment at the ex-plosion site all affect the nature and ex-tent of the damage a mine causes Vic-tims suffer from a broad range ofinjuries Nevertheless, four general pat-terns are recognizable I apologize if thedescription I shall offer of those injuries

is disturbing to many readers Yet tograsp how truly awful these weaponsare, one must be aware of what they doand how they do it

Small blast mines, having diameters

of less than 10 centimeters, produce avery common pattern of injury that wecall Pattern A Among the most com-mon mines in this group are the Italianscatterable mines TS-50 and SB-33 andthe hand-laid VS-50 and VAR-40, theU.S.-made M14, and the Chinese Type

72 Typically, these weapons amputatethe foot or leg In some cases, only part

of the foot may be blown off, depending

on how the mine was placed and how itwas stepped on In most cases, the inju-ries from these types of mines occur be-low the knee, and no major wounds arepresent higher on the body or on theopposite leg

Larger antipersonnel blast mines, such

as those in the Russian PMN series, ally cause a different type of injury (Pat-tern B) This difference arises in part sim-ply from the discrepancy in the size ofthe weapon The diameter of the “small”VS-50 is 9.0 centimeters, whereas aPMN is 11.2 centimeters The shockwaves from both mines explode out-ward at the same high speed, approxi-mately 6,800 meters per second, seventimes the speed of a high-velocity bul-let But the cone of the explosion—thevolume carrying the explosive force—ismuch wider for the larger mine Thelarge mines also contain much morehigh-quality explosive material A VS-

usu-50, for instance, has 42 grams of TNT; a PMN-2 carries 150 grams ofTNT; and a PMN contains 240 grams.Victims stepping on these large anti-personnel mines invariably suffer a trau-matic amputation Quite often the low-

RDX-er part of the leg is blown off A piece

of the tibia (the large bone in the shin)may protrude from the stump, and theremaining muscles are smashed andpushed upward, giving the injury agrotesque cauliflowerlike appearance

The Horror of Land Mines

PATTERN A INJURIES, suffered by the boy below,

are most often caused by small blast mines,

such as the VS-50 mine shown at the right.

These weapons, less than 10 centimeters in

di-ameter, most often amputate a foot or leg,

de-pending on how they are stepped on Rarely do

they produce wounds higher than the knee or on

the opposite leg.

Patterns of Injuries

Trang 28

Occasionally, the lower leg is blown off

completely, along with the knee Large

wounds are often sustained in the thigh,

the genitals or the buttocks In many

pa-tients the opposite leg is also damaged,

bearing gaping wounds or open

frac-tures As a result, sometimes parts of

both legs are lost Penetrating injuries

of the abdomen or chest are also fairly

common

The Russian PFM-1, the so-called

but-terfly mine, causes a third pattern of

in-jury (Pattern C) This mine earned its

nickname because it sports small wings

that enable it to glide to the ground after

it is released from a helicopter A huge

number of them were dropped during

the conflict in Afghanistan As has

of-ten been pointed out, the PFM-1 is

par-ticularly fiendish because it is a “toy

mine”—a weapon masquerading as a

plaything Specialists insist that the

shape of the PFM-1 is dictated by

func-tion, but the fact remains that it is

at-tractive to children

A unique feature of these mines is that

they are activated by distortion or

cu-mulative pressure on their wings; in

oth-er words, they do not necessarily go off

when first touched In Afghanistan my

co-workers and I were told several times

that a child had taken the butterfly—or

“green parrot,” as the Afghans call it—

and played with it for hours with friends

before any explosion occurred The

term “toy mine” therefore seems totallyjustified In our group’s surgical experi-ence of treating more than 150 victims

of this type of mine, we have never seen

a single injured adult

Technically, the PFM-1 is just

anoth-er type of small, scattanoth-erable blast mine,but because of the peculiar damage itcauses, it deserves a separate descrip-tion The PFM-1 is usually being heldwhen it goes off, so it traumatically am-putates one or both hands at the wrist

In less severe cases, only two or three gers are destroyed Very often the blastdoes further harm to the chest and theface Injuries to one or both eyes are verycommon, producing partial or com-plete blindness

fin-Antipersonnel fragmentation minescause the fourth pattern of injury (Pat-tern D) Within this group are the

“bounding” fragmentation mines, such

as the Italian Valmara-69, the ufactured M16 series and the RussianOZM series These weapons are laid onthe ground but, when triggered, jumpinto the air before exploding so thatthey can disperse their fragments overthe maximum range and to the mostlethal effect Directional fragmentationmines—including the U.S.-made M18A1(or “Claymore”) and the Russian MONand POMZ “stake” mines, which aimtheir projectiles toward a target—are also

U.S.-man-in this class of weapon All these mU.S.-man-ines

are typically operated by trip wires.The defining feature of fragmentation mines is that they fire metallic shardsover a wide area The Valmara-69, forexample, explodes at a height of 50 to

100 centimeters—roughly the level of aman’s waist—and projects some 1,000bits of metallic shrapnel across a 360-degree spread Mine specialists considerthis mine to have a “killing zone” with

a 25-meter radius and an “injury zone”

of up to 200 meters

Fragmentation mines produce ies throughout the body The size of thewound depends in part on the size ofthe penetrating splinter If the victim ismeters away from the site of the explo-sion, the fragments will frequently pen-etrate the abdomen, the chest or thebrain, particularly if a bounding mine isinvolved For shorter distances, the in-juries resemble those of Pattern B Still,doctors rarely treat traumatic amputa-tions caused by fragmentation minesbecause the weapons usually kill in aninstant anyone who activates them bydirect contact

injur-In northern Iraq, during the PersianGulf War, for instance, we observed sixcasualties from the explosion of a Val-mara-69 The two persons who weretrying to defuse the mine to recover itsaluminum content—worth about $1 onthe local market—were immediatelykilled At the same time, four other peo-

PATTERN D INJURIES indicate that a person has tripped a fragmentation mine, such as the POMZ-2 “stake” mine above These mines usually kill anyone who comes into direct contact with them by discharging metallic shards over a wide area.

PATTERN C INJURIES are produced by the PFM-1, the so-called fly mine ( left) These mines explode only after cumulative pressure has been applied to their wings, which help them initially to glide to the ground after being released from a helicopter Because they are usually being handled when they go off, these mines amputate fingers or hands and damage the face and chest as well Almost all victims are children, such as the one shown above, who treat the mines as toys.

butter-PATTERN B INJURIES, sustained

by some of the children shown

at the left at the Red Cross

hos-pital in Kabul, Afghanistan,

re-sult from stepping on

antiper-sonnel mines such as the PMN

(above) These mines are not

much larger than small blast

mines, but they pack far more

explosive material As a result,

they often blow off the lower leg

and cause fur ther harm to the

thighs, genitals or buttocks.

Trang 29

ple nearby, including two young

shep-herds, were severely injured Only two

of them survived

The Challenge of Treating Victims

The injury patterns I have described

identify the prevalent distribution

of wounds that a patient may suffer,

but they do not correspond cleanly to

levels of severity A traumatic

amputa-tion of the foot with only a small wound

in the thigh—a Pattern A casualty—

might be life-threatening if the thigh

in-jury involves the femoral artery

Com-monly, the patient who sustains a

land-mine injury is in critical condition Often

a vital structure is directly damaged, or

the wounds (including the traumatic

amputations) are so extensive that the

patient is imperiled by hemorrhagic

shock In such an emergency situation,

identifying a pattern of injury with a

specific category of land mine can

pro-vide useful information to the surgical

team (and also to any personnel

in-volved in clearing the area of mines)

For several reasons, surgery on mine

injuries is a complex and challenging

discipline Often the medical team has

to work in hazardous areas where the

fighting is ongoing The available

facili-ties are typically primitive Scarce

re-sources, the lack of proper hygiene, and

sometimes even the absence of water

and electricity make the job extremely

difficult Furthermore, the surgeons

must be trained to deal with all kinds of

emergencies: vascular, thoracic,

abdom-inal, orthopedic and so on Fragments

of bone, for example, can become

“sec-ondary bullets.” I once had to

recon-struct the axillary artery in the shoulder

of a patient that had been completely

severed by a piece of bone from the

pa-tient’s traumatically amputated foot

From the technical point of view, the

keystone operation is the debridement,

or surgical cleansing, of the wound

When a blast mine goes off, stones,

mud, grass and even pieces of the

pa-tient’s clothes or shoes can be pushed

deep into the tissues by the ascending

explosion The removal of all foreign

The Horror of Land Mines

COUNTRIES reporting land-mine

inci-dents are shaded on the map at the right.

The bar chart shows the number of mines

planted in regions only where such

esti-mates are known The boxes (left )

indi-cate the density of deployed land mines in

those regions, measured as the average

number of mines per square mile

AVERAGE NUMBER OF LAND MINES DEPLOYED PER SQUARE MILE

TOTAL NUMBER OF LAND MINES DEPLOYED

IN MILLIONS

Trang 30

bodies and, even more important, the

excision of all dead, dying or weakened

tissue from the lesions are of paramount

importance in preventing

life-threaten-ing postsurgical infections

A Deadly Legacy

Most patients who recover from

land-mine accidents never truly

regain their ability to take an active part

in family life or society Rehabilitating

these patients under the best

circum-stances is often immensely problematic

And many victims live in developing

countries, where poor living conditions

make it even more difficult to overcome

physical and psychological handicaps

Moreover, beyond the tremendous

hu-man cost that mines claim in lives and

suffering, they also impose a severe

cial and economic burden on entire

so-cieties and nations An army’s decision

to mine agricultural land has long-term

devastating effects on farming nities, who rely on the land for survival

commu-The presence of land mines also detersmany wartime refugees from returning

to their homes The displaced peopletend to become permanent refugees whooverload the economic and social struc-tures of the regions to which they flee

In 1980 the U.N adopted what iscommonly known as the Convention

on Inhumane Weapons Although thisconvention and its protocols were sup-posed to guarantee protection to civil-ians, events during the rest of that de-cade demonstrated all too clearly theinadequacy of those regulations In re-cent years, more than 400 humanitari-

an organizations in nearly 30 countrieshave launched a campaign to raise theinternational community’s awareness ofthe devastating effects of antipersonnelmines They have urged the U.N andnational governments to ban the pro-duction, stockpiling, sale, export and use

of mines The campaign has had cant results, and several countries havedecided to stop the production or ex-port of land mines, at least temporarily

signifi-In September 1995 a U.N review ference of the convention gathered inVienna International diplomacy focusedthe discussion on various technical andmilitary aspects of land-mine use From

con-a humcon-anitcon-aricon-an point of view, the

Vien-na conference was a fiasco A total ban

on these indiscriminate weapons—theonly real solution—was not even takeninto consideration Moreover, it seemsunlikely that a ban will be proposed inthe session of the conference that is cur-rently under way in Geneva Certainlymost countries and citizens of the worldnow realize the horrors of nuclearbombs It is astonishing that those samecountries do not object to the daily mas-sacre of innocent civilians by way ofantipersonnel mines

Still, the world in the next century

fac-es a terrible legacy Many of the minfac-esdropped decades ago may have effectivelifetimes of centuries Indeed, even if nomore mines are laid in the future, thosethat are already in place will cause colos-sal tragedy and will challenge relief or-ganizations of tomorrow We may hopethat the international community willsoon make the issue of land mines a toppriority and provide the funds needed

to carry on essential humanitarian tivities Emergency surgical assistanceand the subsequent rehabilitation of vic-tims, as well as operations to clear minesand to educate people about their dan-gers, will in fact remain the only optionsfor easing the suffering of hundreds ofthousands of people Even for a veteranwar surgeon, looking at the body of achild torn to pieces by these inhumaneweapons is startling and upsetting Thiscarnage has nothing to do with militarystrategy It is a deliberate choice to in-flict monstruous pain and mutilation It

ac-is a crime against humanity

The Author

GINO STRADA received his medical degree from the

University of Milan In 1988 he joined the International

Committee of the Red Cross mission in Pakistan and has

worked as a war surgeon ever since He has treated

land-mine victims in Afghanistan, Cambodia, Peru, Bosnia,

Dji-bouti, Somalia, Ethiopia, Rwanda and northern Iraq In

1994 Strada founded EMERGENCY, a humanitarian

associa-tion serving civilian war victims For more informaassocia-tion,

contact EMERGENCY, via Bagutta 12, 20121 Milan, Italy;

telephone: 39-2-7600-1104; fax: 39-2-7600-3719.

Further Reading

Hidden Killers: The Global Problem with Uncleared Landmines: A Report on International Demining Political-Military Affairs Bureau Office of International Security Operations U.S Department of State, 1993 Landmines: A Deadly Legacy The Arms Project of Human Rights Watch and Physicians for Human Rights Human Rights Watch, 1993.

Social Consequences of Widespread Use of Landmines Jody Williams

in ICRC Report of the Symposium on Anti-personnel Mines ICRC,

Gene-va, 1993.

Ten Million Tragedies, One Step at a Time Jim Wurst in Bulletin of the

Atomic Scientists, Vol 49, No 6, pages 14–21; July–August 1993.

Trang 31

After the discovery of Pluto in 1930, many astronomers became intrigued by the

possibility of finding a 10th planet circling the sun Cloaked by the vast

dis-tances of interplanetary space, the mysterious “Planet X” might have

re-mained hidden from even the best telescopic sight, or so these scientists reasoned Yet

decades passed without detection, and most researchers began to accept that the solar

system was restricted to the familiar set of nine planets

But many scientists began seriously rethinking their notions of the solar system in

1992, when we identified a small celestial body—just a few hundred kilometers

across—sited farther from the sun than any of the known planets Since that time, we

have identified nearly three dozen such objects circling through the outer solar system

A host of similar objects is likely to be traveling with them, making up the so-called

Kuiper belt, a region named for Dutch-American astronomer Gerard P Kuiper, who,

in 1951, championed the idea that the solar system contains this distant family

What led Kuiper, nearly half a century ago, to believe the disk of the solar system

was populated with numerous small bodies orbiting at great distances from the sun?

The Kuiper Belt

Rather than ending abruptly at the orbit of Pluto, the

outer solar system contains an extended belt of small bodies

by Jane X Luu and David C Jewitt

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OUTER EXTREMITIES of the solar system preserve primordial material maining from the time the planets first formed During that early era, Pluto (foreground) may have captured its satellite, Charon (right), while casting a third body (top) away into space At the time, the region would have been

re-thick with dust and rife with growing Kuiper belt objects

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His conviction grew from a

fundamen-tal knowledge of the behavior of certain

comets—masses of ice and rock that on

a regular schedule plunge from the

out-er reaches of the solar system inward

toward the sun Many of these

compar-atively small objects periodically

pro-vide spectacular appearances when thesun’s rays warm them enough to drivedust and gas off their surfaces into lu-minous halos (creating large “comae”)and elongate tails

Astronomers have long realized thatsuch active comets must be relatively

new members of the inner solar system

A body such as Halley’s comet, whichswings into view every 76 years, losesabout one ten-thousandth of its mass oneach visit near the sun That comet willsurvive for only about 10,000 orbits,lasting perhaps half a million years inall Such comets were created during theformation of the solar system 4.5 billionyears ago and should have completelylost their volatile constituents by now,leaving behind either inactive, rockynuclei or diffuse streams of dust Whythen are so many comets still around todazzle onlookers with their displays?

Guiding Lights

The comets that are currently activeformed in the earliest days of thesolar system, but they have since beenstored in an inactive state—most of thempreserved within a celestial deep freezecalled the Oort cloud The Dutch astron-omer Jan H Oort proposed the exis-tence of this sphere of cometary materi-

al in 1950 He believed that this cloudhad a diameter of about 100,000 astro-nomical units (AU—a distance defined

as the average separation between Earthand the sun, about 150 million kilome-ters) and that it contained several hun-dred billion individual comets In Oort’sconception, the random gravitationaljostling of stars passing nearby knockssome of the outer comets in the cloudfrom their stable orbits and gradually de-flects their paths to dip toward the sun.For most of the past half a century,Oort’s hypothesis neatly explained thesize and orientation of the trajectoriesthat the so-called long-period comets

The Kuiper Belt

GRAVITY OF THE PLANETS acted during the early stages of

the solar system to sweep away small bodies within the orbit of

Neptune Some of these objects plummeted toward the sun;

oth-ers sped outward toward the distant Oort cloud (not shown).

100 ASTRONOMICAL UNITS

SUN NEPTUNE

COUNTLESS OBJECTS in the Kuiper belt may orbit far from the sun, but not all of

those bodies can be seen from Earth Objects (circles) that could reasonably be

detect-ed with the telescope on Mauna Kea in Hawaii typically lie near the inner border of the

belt, as seen in this computer simulation of the distribution of distant matter.

NEPTUNE

URANUS KUIPER BELT

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(those that take more than 200 years to

circle the sun) follow Astronomers find

that those bodies fall into the planetary

region from random directions—as

would be expected for comets

originat-ing in a spherical repository like the

Oort cloud In contrast, Oort’s

hypoth-esis could not explain short-period

com-ets that normally occupy smaller orbits

tilted only slightly from the orbital plane

of Earth—a plane that astronomers call

the ecliptic

Most astronomers believed that the

short-period comets originally traveled

in immense, randomly oriented orbits

(as the long-period comets do today)

but that they were diverted by the

grav-ity of the planets—primarily Jupiter—

into their current orbital configuration

Yet not all scientists subscribed to this

idea As early as 1949, Kenneth Essex

Edgeworth, an Irish gentleman-scientist

(who was not affiliated with any

re-search institution) wrote a scholarly

ar-ticle suggesting that there could be a

flat ring of comets in the outer solar

sys-tem In his 1951 paper, Kuiper also

dis-cussed such a belt of comets, but he did

not refer to Edgeworth’s previous work

Kuiper and others reasoned that the

disk of the solar system should not end

abruptly at Neptune or Pluto (which vie

with each other for the distinction of

being the planet most distant from the

sun) He envisioned instead a belt

be-yond Neptune and Pluto consisting of

residual material left over from the

for-mation of the planets The density of

matter in this outer region would be so

low that large planets could not have

accreted there, but smaller objects,

per-haps of asteroidal dimensions, might

exist Because these scattered remnants

of primordial material were so far from

the sun, they would maintain low

sur-face temperatures It thus seemed likely

that these distant objects would be

com-posed of water ice and various frozen

gases—making them quite similar (if not

identical) to the nuclei of comets

Kuiper’s hypothesis languished until

the 1970s, when Paul C Joss of the

Mas-sachusetts Institute of Technology began

to question whether Jupiter’s gravitycould in fact efficiently transform long-period comets into short-period ones

He noted that the probability of tational capture was so small that thelarge number of short-period comets thatnow exists simply did not make sense

gravi-Other researchers were, however, able to confirm this result, and the Oortcloud remained the accepted source ofthe comets, long and short period alike

un-But Joss had sown a seed of doubt,and eventually other astronomers start-

ed to question the accepted view In

1980 Julio A Fernández (then at theMax Planck Institute for Aeronomy inKatlenburg-Lindau) had, for example,done calculations that suggested thatshort-period comets could come fromKuiper’s proposed trans-Neptuniansource In 1988 Martin J Duncan of the

University of Toronto, Thomas Quinnand Scott D Tremaine (both at the Ca-nadian Institute for Theoretical Astro-physics) used computer simulations toinvestigate how the giant gaseous plan-ets could capture comets Like Joss, theyfound that the process worked ratherpoorly, raising doubts about the veracity

of this well-established concept for theorigin of short-period comets Indeed,their studies sounded a new alarm be-cause they noted that the few cometsthat could be drawn from the Oort cloud

by the gravitational tug of the majorplanets should be traveling in a spheri-cal swarm, whereas the orbits of theshort-period comets tend to lie in planesclose to the ecliptic

Duncan, Quinn and Tremaine soned that short-period comets musthave been captured from original orbits

SEQUENTIAL CCD EXPOSURES from

1992 revealed Kuiper belt object QB 1

clearly against the background of fixed

stars (middle and bottom) This pair of

images covers only a small part of the

complete CCD frame (top right ) that had

to be analyzed before the authors could

identify QB 1 (arrows) and determine its

orbit (top left ).

QB 1

SUN

URANUS NEPTUNE PLUTO

Trang 35

that were canted only slightly from the

ecliptic, perhaps from a flattened belt of

comets in the outer solar system But

their so-called Kuiper belt hypothesis

was not beyond question In order to

make their calculations tractable, they

had exaggerated the masses of the outer

planets as much as 40 times (thereby

increasing the amount of gravitational

attraction and speeding up the orbital

evolution they desired to examine)

Oth-er astrophysicists wondOth-ered whethOth-er this

computational sleight of hand might

have led to an incorrect conclusion

Why Not Just Look?

Even before Duncan, Quinn and

Tre-maine published their work, we

wondered whether the outer solar

sys-tem was truly empty or instead full of

small, unseen bodies In 1987 we began

a telescopic survey intended to address

exactly that question Our plan was to

look for any objects that might be

pres-ent in the outer solar system using the

meager amount of sunlight that would

be reflected back from such great

dis-tances Although our initial efforts

em-ployed photographic plates, we soon

decided that a more promising approach

was to use an electronic detector (a

charge-coupled device, or CCD)

at-tached to one of the larger telescopes

We conducted the bulk of our survey

using the University of Hawaii’s

2.2-me-ter telescope on Mauna Kea Our

strat-egy was to use a CCD array with this

in-strument to take four sequential, ute exposures of a particular segment

15-min-of the sky We then enlisted a computer

to display the images in the sequence inquick succession—a process astronomerscall “blinking.” An object that shiftsslightly in the image against the back-ground of stars (which appear fixed)will reveal itself as a member of the so-lar system

For five years, we continued the searchwith only negative results But the tech-nology available to us was improving

so rapidly that it was easy to maintainenthusiasm (if not funds) in the contin-uing hunt for our elusive quarry OnAugust 30, 1992, we were taking thethird of a four-exposure sequence whileblinking the first two images on a com-puter We noticed that the position ofone faint “star” appeared to move slight-

ly between the successive frames Weboth fell silent The motion was quitesubtle, but it seemed definite When wecompared the first two images with thethird, we realized that we had indeedfound something out of the ordinary Itsslow motion across the sky indicatedthat the newly discovered object could

be traveling beyond even the outerreaches of Pluto’s distant orbit Still, wewere suspicious that the mysterious ob-ject might be a near-Earth asteroid mov-ing in parallel with Earth (which mightalso cause a slow apparent motion) Butfurther measurements ruled out thatpossibility

We observed the curious body again

on the next two nights and obtained curate measurements of its position,brightness and color We then commu-nicated these data to Brian G Marsden,director of the International Astronom-ical Union’s Central Bureau of Astro-nomical Telegrams at the SmithsonianAstrophysical Observatory in Cam-bridge, Mass His calculations indicat-

ac-ed that the object we had discoverac-ed wasindeed orbiting the sun at a vast distance(40 AU)—only slightly less remote than

we had first supposed He assigned thenewly discovered body a formal, if some-what drab, name based on the date ofdiscovery: he christened it “1992 QB1.”

(We preferred to call it “Smiley,” afterJohn Le Carré’s fictional spy, but thatname did not take hold within the con-servative astronomical community.)Our observations showed that QB1reflects light that is quite rich in red huescompared with the sunlight that illumi-nates it This odd coloring matched onlyone other object in the solar system—apeculiar asteroid or comet called 5145Pholus Planetary astronomers attributethe red color of 5145 Pholus to the pres-ence of dark, carbon-rich material onits surface The similarity between QB1and 5145 Pholus thus heightened ourexcitement during the first days after thediscovery Perhaps the object we hadjust located was coated by some kind ofred material abundant in organic com-pounds How big was this ruddy newworld? From our first series of measure-ments, we estimated that QB1was be-

The Kuiper Belt

2060 CHIRON may have escaped from the Kuiper belt into its current

planet-crossing orbit (left) Although quite faint, the subtle glow rounding 2060 Chiron ( far right) marks this object as a celestial cous-

sur-in to other “active” bodies, such as Comet Peltier (above).

2060 CHIRON

SATURN SUN

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tween 200 and 250 kilometers across—

about 15 times the size of the nucleus

of Halley’s comet

Some astronomers initially doubted

whether our discovery of QB1truly

sig-nified the existence of a population of

objects in the outer solar system, as

Kui-per and others had hypothesized But

such questioning began to fade when we

found a second body in March 1993

This object is as far from the sun as QB1

but is located on the opposite side of the

solar system During the past three years,

several other research groups have

joined the effort, and a steady stream of

discoveries has ensued The current

count of trans-Neptunian, Kuiper belt

objects is 32

The known members of the Kuiper

belt share a number of characteristics

They are, for example, all located

be-yond the orbit of Neptune, suggesting

that the inner edge of the belt may be

defined by this planet All these newly

found celestial bodies travel in orbits

that are only slightly tilted from the

ecliptic—an observation consistent with

the existence of a flat belt of comets

Each of the Kuiper belt objects is

mil-lions of times fainter than can be seen

with the naked eye The 32 objects range

in diameter from 100 to 400 kilometers,

making them considerably smaller than

both Pluto (which is about 2,300

kilo-meters wide) and its satellite, Charon,

(which measures about 1,100

kilome-ters across)

The current sampling is still quite

mod-est, but the number of new solar systembodies found so far is sufficient to estab-lish beyond doubt the existence of theKuiper belt It is also clear that the belt’stotal population must be substantial Weestimate that the Kuiper belt contains atleast 35,000 objects larger than 100 kilo-meters in diameter Hence, the Kuiperbelt probably has a total mass that ishundreds of times larger than the well-known asteroid belt between the orbits

of Mars and Jupiter

Cold Storage for Comets

The Kuiper belt may be rich in rial, but can it in fact serve as thesupply source for the rapidly consumedshort-period comets? Matthew J Hol-man and Jack L Wisdom, both then atM.I.T., addressed this problem usingcomputer simulations They showedthat within a span of 100,000 years thegravitational influence of the giant gas-eous planets ( Jupiter, Saturn, Uranusand Neptune) ejects comets orbiting intheir vicinity, sending them out to thefarthest reaches of the solar system But

mate-a substmate-antimate-al percentmate-age of trmate-ans-Nep-tunian comets can escape this fate andremain in the belt even after 4.5 billionyears Hence, Kuiper belt objects locat-

trans-Nep-ed more than 40 AU from the sun arelikely to have held in stable orbits sincethe formation of the solar system

Astronomers also believe there hasbeen sufficient mass in the Kuiper belt

to supply all the short-period comets

that have ever been formed So the per belt seems to be a good candidatefor a cometary storehouse And the me-chanics of the transfer out of storage isnow well understood Computer simu-lations have shown that Neptune’s grav-ity slowly erodes the inner edge of theKuiper belt (the region within 40 AU ofthe sun), launching objects from thatzone into the inner solar system Ulti-mately, many of these small bodies slow-

Kui-ly burn up as comets Some—such asComet Shoemaker-Levy 9, which collid-

ed with Jupiter in July 1994—may endtheir lives suddenly by striking a planet(or perhaps the sun) Others will becaught in a gravitational slingshot thatejects them into the far reaches of inter-stellar space

If the Kuiper belt is the source of period comets, another obvious questionemerges: Are any comets now on theirway from the Kuiper belt into the innersolar system? The answer may lie in theCentaurs, a group of objects that in-cludes the extremely red 5145 Pholus.Centaurs travel in huge planet-crossingorbits that are fundamentally unstable.They can remain among the giant plan-ets for only a few million years beforegravitational interactions either sendthem out of the solar system or transferthem into tighter orbits

short-With orbital lifetimes that are farshorter than the age of the solar system,the Centaurs could not have formedwhere they currently are found Yet thenature of their orbits makes it practical-

Trang 37

ly impossible to deduce their place of

origin with certainty Nevertheless, the

nearest (and most likely) reservoir is the

Kuiper belt The Centaurs may thus be

“transition comets,” former Kuiper belt

objects heading toward short but showy

lives within the inner solar system The

strongest evidence supporting this

hy-pothesis comes from one particular

Cen-taur—2060 Chiron Although its

discov-erers first thought it was just an

unusu-al asteroid, 2060 Chiron is now firmly

established as an active comet with a

weak but persistent coma

As astronomers continue to study the

Kuiper belt, some have started to

won-der whether this reservoir might have

yielded more than just comets Is it

co-incidence that Pluto, its satellite,

Char-on, and the Neptunian satellite Triton

lie in the vicinity of the Kuiper belt? Thisquestion stems from the realization thatPluto, Charon and Triton share similar-ities in their own basic properties butdiffer drastically from their neighbors

A Peculiar Trio

The densities of both Pluto and ton, for instance, are much higherthan any of the giant gaseous planets ofthe outer solar system The orbital mo-tions of these bodies are also quitestrange Triton revolves around Neptune

Tri-in the “retrograde” direction—opposite

to the orbital direction of all planetsand most satellites Pluto’s orbit slantshighly from the ecliptic, and it is so farfrom circular that it actually crosses theorbit of Neptune Pluto is, however, pro-

tected from possible collision with thelarger planet by a special orbital rela-tionship known as a 3:2 mean-motionresonance Simply put, for every threeorbits of Neptune around the sun, Plu-

to completes two

The pieces of the celestial puzzle mayfit together if one postulates that Pluto,Charon and Triton are the last survivors

of a once much larger set of similarlysized objects S Alan Stern of the South-west Research Institute in Boulder firstsuggested this idea in 1991 These threebodies may have been swept up by Nep-tune, which captured Triton and lockedPluto—perhaps with Charon in tow—into its present orbital resonance.Interestingly, orbital resonances ap-pear to influence the position of manyKuiper belt objects as well Up to onehalf of the newly discovered bodies havethe same 3:2 mean-motion resonance

as Pluto and, like that planet, may orbitserenely for billions of years (The reso-nance prevents Neptune from approach-ing too closely and disturbing the orbit

of the smaller body.) We have dubbedsuch Kuiper belt objects Plutinos—“lit-tle Plutos.” Judging from the small part

of the sky we have examined, we mate that there must be several thou-sand Plutinos larger than 100 kilome-ters across

esti-The recent discoveries of objects inthe Kuiper belt provide a new perspec-tive on the outer solar system Pluto nowappears special only because it is largerthan any other member of the Kuiperbelt One might even question whetherPluto deserves the status of a full-fledgedplanet Strangely, a line of research thatbegan with attempts to find a 10th plan-

et may, in a sense, have succeeded in ducing the final count to eight Thisirony, along with the many intriguingobservations we have made of Kuiperbelt objects, reminds us that our solarsystem contains countless surprises

re-The Kuiper Belt

The Authors

JANE X LUU and DAVID C JEWITT came to study astronomy in

dif-ferent ways For Jewitt, astronomy was a passion he developed as a

young-ster in England Luu’s childhood years were filled with more practical

con-cerns: as a refugee from Vietnam, she had to learn to speak English and

ad-just to life in southern California She became enamored of astronomy

almost by accident, during a summer spent at the Jet Propulsion Laboratory

in Pasadena Luu and Jewitt began their collaborative work in 1986 at the

Massachusetts Institute of Technology Jewitt was a professor there when

Luu became a graduate student Jewitt moved to the University of Hawaii

in 1988 It was during Luu’s postdoctoral fellowship at the

Harvard-Smith-sonian Center for Astrophysics that Luu and Jewitt discovered the first

Kui-per belt object In 1994 Luu joined the faculty of Harvard University.

MEAN-MOTION RESONANCE governs the size and shape of the orbits of many

Kuiper belt objects Orbits are described by eccentricity (deviation from circularity) and

semimajor axis (red arrow) Like Pluto, about half the known Kuiper belt bodies (red

points) circle the sun twice while Neptune completes three orbits—a 3:2 resonance The

object 1995 DA 2 orbits in one of the other resonances Renu Malhotra of the Lunar

and Planetary Institute in Houston suggests that this pattern reflects the early evolution

of the solar system, when many small bodies were ejected and the major planets

mi-grated away from the sun During these outward movements, Neptune could have drawn

Pluto and a variety of smaller bodies into the resonant orbits that are now observed.

Further Reading

The Origin of Short Period Comets Martin Duncan,

Thomas Quinn and Scott Tremaine in Astrophysical

Jour-nal, Vol 328, pages L69–L73; May 15, 1988.

The Kuiper Belt Objects J X Luu in Asteroids, Comets,

Meteors 1993 Edited by A Milani, M Di Martino and A.

Cellino Kluwer Academic Publishers, 1993.

The Solar System beyond Neptune D C Jewitt and J.

X Luu in Astronomical Journal, Vol 109, No 4, pages

Trang 38

Imagine that well before tumors

arose in people, a laboratory could

detect biological clues, or

biomark-ers, indicating that tissues had been

as-saulted by specific cancer-causing agents

or, worse, were beginning to undergo

precancerous changes And suppose it

were possible to identify biomarkers of

special vulnerability to the effects of

carcinogens in the environment (These

agents can include tobacco smoke,

ra-diation, certain microbes, and natural

and synthetic chemicals in our food,

wa-ter and air.) Discovery of such markers

could help affected individuals to

pre-vent cancer, in part because they would

know which carcinogens they most

needed to avoid Use of markers to

demonstrate heightened risk in certain

groups, such as children, might also

spur public health officials to take new

measures to reduce exposures that are

beyond an individual’s control

With such aims in mind, researchers

in a burgeoning discipline called

molec-ular epidemiology have begun looking

for biomarkers that can signal enhanced

risk for cancer The field is still young

Scientists cannot yet screen for a panel

of markers in an individual and then

of-fer a meaningful assessment of the

per-son’s likelihood of acquiring cancer

Nevertheless, such testing should one

day be feasible (The delay is not all bad

People who undergo screening will need

to be carefully protected from

discrimi-nation by insurance companies and

em-ployers, but the needed safeguards are

not yet in place.)

In the meantime, the available data

are proving to be informative in other

ways In particular, they are lending

sup-port to the view that current methods

for determining “acceptable” levels of

exposure to environmental carcinogensmay seriously underestimate the dangerfaced by some segments of society Bio-markers may also soon be useful to re-searchers interested in developing newapproaches to preventing cancer Instead

of waiting years or decades to learnwhether exposure to some chemical in-creases cancer rates in humans or wheth-

er an experimental intervention reducesincidence, investigators may be able toattain relatively quick answers by mon-itoring selected signs of precancerousdamage in the body

Epidemiology with a Difference

Molecular epidemiology resemblesconventional epidemiology butdiffers in important ways as well It com-bines the tools of standard epidemiology(such as case histories, questionnaires,and monitoring of exposure) with thesensitive laboratory techniques of mo-lecular biology The conventional ap-proach by itself has made major contri-butions to the understanding of cancerrisk For instance, traditional epidemi-ology has shown that high-fat diets canplay a part in colon cancer, has linkedbenzene to leukemia and has establishedthat cigarette smoking profound-

ly increases the chance ofacquiring lung cancer Ithas even quantified risks:

one in 10 heavy smokers islikely to get lung cancer But such re-search reveals nothing about the precisecontinuum of events leading from ex-posure to overt disease Molecular epi-demiology aims to uncover critical pre-cancerous events taking place inside thebody and to identify measurable bio-logic flags signaling their occurrence

Uncovering New Clues

to Cancer Risk

A growing discipline called molecular epidemiology is attempting

to find early biological signposts for heightened risk of cancer

The research should enhance prevention of the disease

by Frederica P Perera

Enhanced activation,

or inefficient detoxification,

of carcinogens

CARCINOGEN ENTERS BODY

Polycyclic aromatic hydrocarbons (PAHs)

in smoke or air

MARKER OF SUSCEPTIBILITY

PATHWAY TO DISEASE

Uncovering New Clues to Cancer Risk

Trang 39

This work is informed by, and is

con-tributing to, a growing understanding

of how cancer develops It now seems

clear that malignancies generally arise

through the serial accumulation of

dam-age to genes in a single cell When the

collected defects finally free the cell from

normal restraints on growth, tumors

develop and, all too often, invade

near-by tissue and establish lethal satellites(metastases) elsewhere in the body

The discovery that genetic damage lies

at the root of cancer does not mean mostmalignancies stem from the inheritance

of seriously flawed genes In fact, suchinheritance probably explains no morethan 5 percent of all cancers in the U.S

The genetic disruptions that transform

a normal cell into a malignant one cally arise in the course of living—viacomplex interactions between carcino-gens and the body’s systems for con-tending with them (The offending car-cinogens include those in the environ-ment and those, called oxidants, thatour bodies generate during normal me-tabolism.) Indeed, whether any agent

typi-Low

levels of

antioxidants

Inefficient repair

of DNA

Inefficient immune recognition

of malignant cells VARIOUS TRAITS CAN INCREASE LIKELIHOOD OF TUMOR DEVELOPMENT

GENETIC MUTATIONS FREE CELL FROM NORMAL RESTRAINTS

ON GROWTH AND DIFFERENTIATION

Lung tumor

DETECTABLE DISEASE APPEARS

Scientific American May 1996 55

MOLECULAR EPIDEMIOLOGY supplies information that

classical epidemiology cannot, as is illustrated here by the

exam-ple of lung cancer Classical epidemiology (top) identifies factors

that increase risk for cancer (such as inhalation of polluted air or

tobacco smoke), but it does not address how the disease arises.

Molecular epidemiology (bottom) looks into the black box to

uncover important steps leading from carcinogenic exposures to

disease It also identifies biological signs, or biomarkers, that

may indicate increased risk Some markers (rectangular flags)

reflect exposure or advancement along the pathway to cancer Others reflect innate or acquired susceptibility to the effects of

carcinogens (small banners) By detecting such markers,

re-searchers may one day be able to pinpoint groups or individuals who most need preventive interventions.

Trang 40

contributes to cancer depends not only

on the extent of an individual’s

expo-sure but also on the effectiveness of the

body’s defensive responses—responses

now known to vary from one

individu-al to another, sometimes profoundly

In the early 1980s my colleagues and

I at Columbia University laid out the

basic conceptual framework for

molec-ular epidemiological investigations of

cancer after we detected a new

molec-ular marker indicating that a specific

carcinogen had damaged DNA in

hu-man tissue Simply put, molecular

epi-demiologists probe samples of human

tissue for biologic markers that reflect

exposure to a carcinogen,

cancer-induc-ing damage to cells or tissue, or special

vulnerability to carcinogens Through a

series of steps, these markers are

“vali-dated,” tested to show that they

indi-cate an increased risk for cancer well

be-fore clinical signs appear Valid markers

(those that pass many such tests) can

then be measured in selected groups

and can signal a need for intervention

The steps by which we found a new

marker and established its potential

val-ue as a warning of increased risk for lung

cancer serve to exemplify the overall

ap-proach In 1982, working with I

Ber-nard Weinstein of Columbia and

Miri-am C Poirier of the National Cancer

In-stitute, I noted that a well-known class

of carcinogens—polycyclic aromatic

hy-drocarbons (PAHs)—left a unique gerprint” in human lung and blood cells

“fin-These hydrocarbons are among the proximately 400 chemicals that havebeen shown to be carcinogenic in stud-ies of animals or humans; they are com-bustion products found mainly in tobac-

ap-co smoke, polluted air, and barbecued,grilled or smoked foods The fingerprinttook the form of an adduct, a complexthat results when a chemical attaches to

a biological molecule, usually to DNA

as early markers of an increased pensity for lung cancer My colleaguesand I, including Regina M Santella ofColumbia and Kari Hemminki of theKarolinska Institute in Stockholm, dem-onstrated that people known to havebeen exposed to high levels of PAHs intobacco smoke, in polluted air and atcertain work sites displayed markedlyhigher levels of PAH-DNA adducts intheir blood than did people whose ex-posure was lower

pro-These findings could not by themselvestell us whether the adducts signified aheightened likelihood that lung cancerwould develop, but subsequent studiessupported that idea Subjects who har-

bored high levels of PAH-DNA plexes and related adducts in the bloodalso suffered greater than normal levels

com-of genetic mutations and other somal disturbances in blood cells Be-cause such changes are common in ma-lignant cells, the results were consistentwith the notion that increased quanti-ties of the adducts could reflect addedliability for cancer

chromo-Further circumstantial evidence camefrom our finding that blood samplesfrom patients with lung cancer containmarkedly higher amounts of PAH-DNAadducts than do samples drawn fromcancer-free individuals who have beenexposed to similar doses of lung carcino-gens We are now analyzing stored bloodsamples from volunteers enrolled in along-term study to determine whetherPAH-DNA adducts and other markersare able to predict lung cancer years be-fore diagnosis

Markers of Exposure and Damage

Anumber of other biomarkers show promise for detecting heightenedrisk of cancer, including that of the liverand the bladder For instance, it is wellknown that a natural substance calledaflatoxin B1 (common in moldy corn

FOUNDRY WORKERS ( photograph), smokers and people who live in highly

indus-trial regions often breathe in high levels of combustion products, including carcinogens

known as polycyclic aromatic hydrocarbons (PAHs) “Fingerprints” of this exposure

can be detected in lung and blood cells, in the form of PAH-DNA adducts:

DNA-dam-aging complexes arising when such hydrocarbons ( red in computer-generated image

at left ) bind to DNA ( green) Adducts in white blood cells of one exposed individual

appear as green fluorescence in the micrograph at the right.

Tiêu đề	The Lost Technology of Ancient Greek Rowing
Tác giả	John R. Hale
Trường học	Unknown University or Institution
Chuyên ngành	Science and History
Thể loại	Essay
Năm xuất bản	1996

Định dạng
Số trang	91
Dung lượng	8,35 MB